Email

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Email

Spam

Spamassassin

Set spamassassin for automatically delete junkmail. You can change the "days" that spamassassin sets to automatically delete junkmail, to delete after two months 

db configuration setprop spamassassin MessageRetentionTime 60  
signal-event email-update


The "Custom spam rejection level" will only work when "Spam sensitivity" is set to custom.

  1. Open server-manager.
  2. Click e-mail in the navigation pane (left-hand side).
  3. Click Change e-mail filtering settings.
  4. Change "Spam sensitivity" to custom and adjust the settings to your liking.

This happens because by default, no mail (except for viruses) gets rejected without the admin doing something first.

X-Spam-Level Header in Email Messages

SME does not create an X-Spam-Level header in processed email messages by default.

To enable this capability: 

/usr/bin/yum install --enablerepo=smecontribs smeserver-qpsmtpd-spamassassinlevelstars
signal-event email-update

(Based on Bugzilla:3505)

Custom Rule Scores

You can customize the score assigned by a specific Spamassassin rule (SARE_ADULT2 in this case) as follows: 

mkdir -p /etc/e-smith/templates-custom/etc/mail/spamassassin/local.cf
cd /etc/e-smith/templates-custom/etc/mail/spamassassin/local.cf
echo "score SARE_ADULT2 20.000" >> 20localscores
signal-event email-update

You can now add additional tests and custom scores by editing the newly-created template fragment 20localscores and adding new custom scores using: 

pico -w /etc/e-smith/templates-custom/etc/mail/spamassassin/local.cf/20localscores
signal-event email-update

Each custom score goes on its own line. If you enter a score surrounded by parentheses, the "custom" score will be added to the default score for the specified test (use score TEST_NAME (-1) to reduce the score for 'TEST_NAME' by 1)

You can remove these customizations using: 

rm -f /etc/e-smith/templates-custom/etc/mail/spamassassin/local.cf/20localscores
signal-event email-update

References:

Real-time Blackhole List (RBL)

Enabling RBL's
RBL's are disabled by default to allow maximum accommodation (your ISP may be on a RBL & you may not know it). You can enable RBL's by: 

config setprop qpsmtpd DNSBL enabled RHSBL enabled
signal-event email-update

You can see your RBL's by: 

config show qpsmtpd

You can add to your RBL's by: 

config setprop qpsmtpd RBLList <rbl-list-name>
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Many will argue what's best but most would agree that you can set best-practice recommended settings by: 

config setprop qpsmtpd RBLList zen.spamhaus.org:whois.rfc-ignorant.org:dnsbl.njabl.org
signal-event email-update

Note: More information on this topic can be found here: [1] [2]

Server Only

Some of the spam filter rules cannot work unless the SMESERVER knows the external IP of the box. If you put a SMESERVER in server-only mode behind other firewalls, it will lose some of the anti-spam rules. For example, the rule that blocks attempts where spammers try "HELO a.b.c.d" where a.b.c.d is your external IP address.

Unfortunately, many admins believe that port-forwarding SMTP provides additional security. It doesn't, it limits the SMESERVER's ability to apply some rules.


I want to enable GreyListing

GreyListing support is under the covers and can easily be enabled for those who know what they are doing. However, many experienced users found that they spent more time looking after the greylisting configuration than they received in benefit.

Setup Blacklists & Bayesian Autolearning

(Much of what follows has been shamelessly copied from the Sonoracomm howto)

The default SME settings (as you can see here) do not include DNSBL filtering, spam rejection, or (which is not obvious from the above) bayesian filtering in spamassassin to allow spamassassin to learn from received email and improve over time.

The following command will enable the default blacklists, enable the bayesian learning filter and set thresholds for the bayesian filter. 

config setprop spamassassin UseBayes 1
config setprop spamassassin BayesAutoLearnThresholdSpam 4.00
config setprop spamassassin BayesAutoLearnThresholdNonspam 0.10
expand-template /etc/mail/spamassassin/local.cf
sa-learn --sync --dbpath /var/spool/spamd/.spamassassin -u spamd
chown spamd.spamd /var/spool/spamd/.spamassassin/bayes_*
chown spamd.spamd /var/spool/spamd/.spamassassin/bayes.mutex
chmod 640 /var/spool/spamd/.spamassassin/bayes_* 
config setprop qpsmtpd DNSBL enabled
config setprop qpsmtpd RHSBL enabled
config setprop spamassassin status enabled
config setprop spamassassin RejectLevel 12
config setprop spamassassin TagLevel 4
config setprop spamassassin Sensitivity custom
signal-event email-update

These commands will:

  • enable spamassassin
  • configure spamassassin to reject any email with a score above 12
  • tag spam scored between 4 and 12 in the email header
  • enable bayesian filter
  • 'autolearn' as SPAM any email with a score above 4.00
  • 'autolearn' as HAM any email with a score below 0.10
  • enable RHSBL using the default SBLList. Note that rhsbl checking has been known to place a heavy burden on SME servers.
  • enable DNSBL using the default RBLList

The entire Sonoracomm howto from Google's text cache

  • The Sonoracomm HowTo has been a very well regarded set of instructions for SME mail server configuration for quite a while.
  • This section was created during an extended outage of the Sonoracomm web server (in 2007?)
  • The content below has been modified to include changes suggested in the bug tracker and forums.
  • These instructions are aimed mostly at configuring SME as the only mail server, not for using SME with an internal mail server. (Specifically, LearnAsSpam.pl is harder to configure when using an internal mail server - you would have to develop a method for getting the unmarked SPAM into an IMAP folder directly on the SME server itself. Not impossible, but difficult!)

SONORA COMMUNICATIONS, INC.

This is a quick configuration howto, not an in-depth look at SpamAssassin. Much more can be done beyond this document, but this will take a big dent out of your spam and free up CPU cycles on your server.

See 'More Information' at the end.

SpamAssassin

The following command will enable the default blacklists, enable the bayesian learning filter and set thresholds for the bayesian filter. 

rpm -Uvh \
http://mirror.contribs.org/smeserver/contribs/\
michaelw/sme7/smeserver-spamassassin-features-0.0.2-0.noarch.rpm

This command will install the FuzzyOCR SA plugin designed to catch those nasty image-based spam messages. 

yum -y --enablerepo=smeupdates-testing install FuzzyOcr

Server-Manager

Using the Server-Manager Configuration/E-Mail panel, adjust the settings to these reasonable

  • Virus scanning Enabled
  • Spam filtering Enabled
  • Spam sensitivity Custom
  • Custom spam tagging level 4
  • Custom spam rejection level 12
  • Sort spam into junkmail folder Enabled
  • Modify subject of spam messages Enabled

It is also recommend blocking all executable content. To do so, select (highlight) all of the attachment types other than zip files (the last two).

Click Save.

How It Works

When receiving an incoming message, the server first tests for RBL and DNSBL listings, if enabled. If the sender is blacklisted, the messages are blocked outright and Spamassassin never sees it.

With this configuration, the spammiest messages, those marked as 12 or above, will be rejected at the SMTP level. Those spam messages marked between 4 and 12, will be routed to the users' (IMAP) junkmail folder. This is done so the users can check for false-positives...valid messages that were classified as spam by SpamAssassin.

Users may check their junkmail folders for false-positives via webmail, or, if they are using an IMAP mail client, by simply checking the junkmail folder exposed by their mail client.

https://servername/webmail

Tweaking

The server will automatically delete old spam in the junkmail folders after 90 days. You can control the number of days old spam is kept with the following commands. Where 15 is the number of days you want to keep messages, do... 

db configuration setprop spamassassin MessageRetentionTime 15
signal-event email-update
svc -t /service/qpsmtpd

then 

config show spamassassin

If you think you are losing misclassified mail, adjust the Custom spam rejection level higher.

If too much spam is making through to your inbox, carefully adjust the 'Custom spam tagging level' down. Many people use the level 4. Anything below that may result in false-positives. YMMV.

If too much spam is building up in your (IMAP) junkmail folder, adjust the 'Custom spam rejection level' down or change the number of days spam is kept in the junkmail folder before being automatically deleted by the server.

Bayesian (Learning) Filter

Install the LearnAsSpam.pl, (optional) mailstats and sa-update scripts, then configure nightly cron jobs like this: 

cd /usr/bin
wget http://mirror.contribs.org/smeserver/\
contribs//bread/mailstats/LearnAsSpam.pl
wget http://mirror.contribs.org/smeserver/\
contribs//bread/mailstats/spamfilter-stats-7.pl
cd /etc/cron.d
wget http://mirror.contribs.org/smeserver/\
contribs//bread/mailstats/LearnAsSpam.cron
wget http://mirror.contribs.org/smeserver/\
contribs//bread/mailstats/mailstats.cron
cd /etc/cron.daily
wget http://mirror.contribs.org/smeserver/\
contribs//bread/mailstats/sa-update
chmod +x sa-update
/etc/rc.d/init.d/crond restart

Using an IMAP mail client, create a new folder called 'LearnAsSpam' (case sensitive). It can be created at the top level (like 'Inbox') or as a sub-folder. Create the folder for each user that will help train the Bayesian filter. Webmail will work fine for creating this folder, as well as for checking the junkmail (filtered mail or quarantine) folder.

If any spam messages make it past the filter and into your inbox, just move them into the LearnAsSpam folder. A nightly cron job will process them and delete them for you. This is how you train the Bayesian filter.

Testing

You can check the auto-learning statistics with this command. You will be able to note the accumulation of the spam tokens (or not). Note that the Bayesian filtering must receive 200 spam messages before it starts to function, so don't expect instantaneous results. 

sa-learn --dump magic

You can check the spam filter log with this command: 

tail -50 /var/log/spamd/current | tai64nlocal

If you ever see an error such as: warn: bayes: cannot open bayes databases /etc/mail/spamassassin/bayes_* R/W: tie failed: Permission denied Try adjusting some permissions with these commands: 

chown :spamd /var/spool/spamd/.spamassassin/*
chmod g+rw /var/spool/spamd/.spamassassin/*

Whitelist and Blacklist

If mail comes in and it is misclassified as spam (and moved to the junkmail folder when that feature is enabled), you can add the sender to the whitelist so that future messages coming in from that sender are not filtered.

Conversely, you can add a spammer to the blacklist so you never see their spam again.

Add senders (or their entire domains) to the global whitelist (or blacklist) with commands similar to these (as root): 

db spamassassin setprop wbl.global *@vonage.com White
db spamassassin setprop wbl.global *domain2.com White
db spamassassin setprop wbl.global badname@baddomain.com Black
db spamassassin setprop wbl.global *@verybaddomain.com Black
db spamassassin setprop wbl.global This e-mail address is being protected from spam bots, you need JavaScript enabled to view it White
db spamassassin setprop wbl.global This e-mail address is being protected from spam bots, you need JavaScript enabled to view it Black
expand-template /etc/mail/spamassassin/local.cf
svc -t /service/spamd

You can enter multiple addresses/domains for both white and black lists in one command 

db spamassassin setprop wbl.global name@domain.com White *domain2.com White *domain3.com Black
expand-template /etc/mail/spamassassin/local.cf
svc -t /service/spamd

You can view the lists with this command: 

db spamassassin show

You can delete one or more entries from the white/blacklist using 

db spamassassin delprop wbl.global name@domain.com *domain2.com
  • name@domain.com and *domain2.com must exactly match a value in the output from db spamassassin show to the left of the equals sign.
  • You do not need to specify White or Black when deleting entries.


Clam Antivirus

Update and check your Clam Antivirus with this command. This is normally done automatically every hour via cron. 

freshclam -v

or 

freshclam --debug

Verify hourly update checking by viewing the freshclam/current log file via the Server-Manager View Log Files panel.

Realtime Blackhole Lists and DNS Blacklists

To view the settings for the RBL and DNSBL, use this command: 

config show qpsmtpd

If you followed the instructions above, both checks are enabled.

To see the log of these tests, use a command like: 

tail /var/log/qpsmtpd/current | tai64nlocal

To specify multiple RBLs, use a command like this: 

config setprop qpsmtpd RBLList \
bl.spamcop.net,combined.njabl.org,dnsbl.ahbl.org,dnsbl-1.uceprotect.net,\
list.dsbl.org,multihop.dsbl.org,psbl.surriel.com,zen.spamhaus.org

Note: we have had trouble with the uceprotect.net level 2 list and sometimes remove it from the list as shown here.

To enable or disable both available lists, use something like: 

config setprop qpsmtpd DNSBL enabled RHSBL enabled

To confirm any configuration changes and enact them: 

signal-event email-update
svc -t /service/qpsmtpd

More Information

Introduction to Antispam Practices - here

Here is another great [3] howto.

Informative URLs: 

perldoc Mail::SpamAssassin::Conf

Last Updated ( Thursday, 21 June 2007 )

Email Clients

"concurrency limit reached" when using IMAP

Sometime shows as Thunderbird giving this error message, This Mail-server is not a imap4 mail-server

To workaround thunderbirds limitations change, this thunderbird setting to false

  • Preferences, Advanced, Config editor (aka about:config): filter on tls.
  • set security.enable_tls to false

You can also increase the ConcurrencyLimitPerIP and/or ConcurrencyLimit value for imap and/or imaps (secure) 

config setprop imap ConcurrencyLimitPerIP 20
config setprop imaps ConcurrencyLimitPerIP 20
signal-event post-upgrade; signal-event reboot

check 

config show imap
tail -f /var/log/imap/current | tai64nlocal

More detail can be found here.

Mail server is not an IMAP4 mail server

This is a bug in Thunderbird, the previous tips may help

The Bat

The gives this error message, but they are wrong.
"This server uses TLS v3.0 which is considered to be obsolete and insecure. The server must use TLS v3.1 or above."


Outlook/Outlook Express give error 10060/0x800CCC90

Most likely OUTLOOK (EXPRESS) isn't configured correctly. 

-open OUTLOOK
-click TOOLS > ACCOUNTS
-click CHANGE (on the right-hand side)
-find INCOMING MAIL SERVER & OUTGOING MAIL SERVER (on right-hand side)
-type: mail.yourdomain.tld (in both places)
-click MORE SETTINGS (on bottom-right)
-click OUTGOING SERVER tab (at the top)
-checkmark "MY OUTGOING SERVER REQUIRES AUTHENTICATION"
-bullet "USE SAME SETTINGS AS INCOMING MAIL SERVER"
-click ADVANCED tab (at the top)
-find OUTGOING SERVER
-checkmark "THIS SERVER REQUIRES A SECURE CONNECTION" (under outgoing server)
-change 25 to 465
-[possibly required, secure IMAP is 993]
-click OK > NEXT > FINISHED
-you're finished, your email should work now

Outlook test message doesn't come through

You clicked the TEST ACCOUNT SETTINGS in OUTLOOK didn't you? This is a bug in OUTLOOK. The test message sends a test email with 'no Date header'. As the name suggests, this means a message without any date. Since the server doesn't accept mail with 'no Date header' (because it's required) the message is rejected. To test, send an actual message from OUTLOOK.

If you want, you can try THUNDERBIRD. It's like OUTLOOK but made by a different company. It's completely free and works very well at home and at the office.

I can't receive/send email from my application (ACT!, vTiger, MS Outlook, etc)

Most likely, this is a bug the application you're using and not a problem with the SMESERVER. The application sends an email with 'no Date header'. As the name suggests, this means a message without any date. Since the server doesn't accept mail with 'no Date header' (because it's required) the message is rejected.

As a workaround you can disable the check for the 'Date header'. To disable this check on the internal interface: 

mkdir -p /etc/e-smith/templates-custom/var/service/qpsmtpd/config/peers/local
cd /etc/e-smith/templates-custom/var/service/qpsmtpd/config/peers/local
echo "# 17check_basicheaders disabled by custom template" > \
17check_basicheaders
signal-event email-update

To disable this check for the external interface: 

mkdir -p /etc/e-smith/templates-custom/var/service/qpsmtpd/config/peers/0
cd /etc/e-smith/templates-custom/var/service/qpsmtpd/config/peers/0
echo "# 17check_basicheaders disabled by custom template" > \
17check_basicheaders
signal-event email-update

After I upgrade my SME Server, my email folders have disappeared when using IMAP

After upgrade, if there are missing IMAP folders, the client may need to re-subscribe to folders. This may affect either webmail users or users who use an IMAP email client.

Entourage: Using SME's Self-Signed Certificate for SSL Connections from Entourage on OS X 10.4

The main problem here is that Microsoft has decided that Entourage will only support trusted, PEM Base-64 Encoded certificates. To use IMAPS or SMTPS from Entourage with your SME server, you will need to: 

1. Login to your Mac as a user with administrative privileges

2. Open Safari and browse to https://smeserver/server-manager.  
   When you receive the warning about your certificate:
   - click on "Show Certificate"
   - click and drag the gold-rimmed image of a certificate to your desktop.  
   You will now have myserver.mydomain.tld.cer on your desktop.

3. Locate and open the Microsoft Cert Manager
   - "Import" the certificate you downloaded in step 2.

4. Highlight the imported certificate and "Export" it. 
   - Select the "PEM..." format
   - add "pem." to the beginning of the filename
   - export it to your Desktop

5. Double-click on the new pem.myserver.mydomain.tld.cer  
   - Apple's Keychain Access application will open.
   - Select the X509Anchors Keychain and click "OK"

6. While still in Apple's Keychain Access, select the "Certificates" category
   - Drag pem.myserver.mydomain.tld.cer into the certificates window.

You should now be able to connect to your SME from your Entourage using IMAPS.

If you are accessing your SME server using a different name than the one encoded in the certificate you will still receive a security warning from Entourage, but "OK" will now grant access to your folders.

Notes:

  • Procedure mostly taken from http://www.kerio.com/manual/kmsug/en/ch09s06.html
  • I still get various other IMAP errors due, I suspect, to the "concurrency limit reached" issue.
  • Click on "Show Keychains" in Apple's "Keychain Access" if you need to delete a certificate and try again.

Server Settings

Double bounce messages

To stop admin receiving double bounce messages 

config setprop qmail DoubleBounceTo someoneuser
signal-event email-update

Or just delete them. You risk losing legitimate double bounces (which are rare, but you want to look at them when they do occur) 

config setprop qmail DoubleBounceTo devnull
signal-event email-update

see a longer explaination here

Keep a copy of all emails

You may need to keep a copy of all emails sent to or from your email server. This may be for legal, or other reasons.

The following instructions will create a new user account (maillog) and forward every email that goes through your SME server to it.

First, log onto the server-manager and create the user maillog

Go to the SME Command Line (logon as root) and issue the following commands: 

config setprop qpsmtpd Bcc enabled
signal-event email-update

Optionally make the forwarding of the emails invisible to the end user. Without it, there will be an X-Copied-To: header in each email. Run this command before the signal-event 

config setprop qpsmtpd BccMode bcc

If you want to view the emails, point your email client at the SME and log on as maillog.

Set max email size

Restrict the size of email messages that can pass through your mail server 

config setprop qmail MaxMessageSize x
signal-event email-update

where x is in bytes, eg 6000000 = 6 MB

add the admin user as an administrator for Horde

config setprop horde Administration enabled 
signal-event email-update

Disable mail to a user from an external network

Can be either a user, pseudonym or group 

db accounts setprop groupname/username Visible internal
signal-event email-update

I can't receive mail at: user@mail.domain.tld

Add mail.domain.tld as a virtualdomain. 

-login to SERVER-MANAGER
-click DOMAINS (on the left)
-click ADD
-type: mail.domain.tld

How do I find out who is logged into webmail and what IP number.

This is logged is in /var/log/messages.

How do I enable smtp authentication for users on the internal network.

mkdir -p /etc/e-smith/templates-custom/var/service/qpsmtpd/config/peers/local
cd /etc/e-smith/templates-custom/var/service/qpsmtpd/config/peers/local
cp /etc/e-smith/templates/var/service/qpsmtpd/config/peers/0/05auth_cvm_unix_local .
signal-event email-update

(note the "." at the end of the 3rd line)
Authentication for the local network will now follow the setting of config::qpsmtpd::Authentication

How do I disable SMTP relay for unauthenticated LAN clients

http://forums.contribs.org/index.php?topic=38797.msg176490#msg176490

  • Enable smtp authentication as shown above
  • Disable un-authenticated smtp relay for the local network(s)using:
mkdir -p /etc/e-smith/templates-custom/var/service/qpsmtpd/config/relayclients
echo "# SMTP Relay from local network denied by custom template" >\
/etc/e-smith/templates-custom/var/service/qpsmtpd/config/relayclients/80relayFromLocalNetwork
signal-event email-update
  • Configure your email clients to use smtps with authentication:

- change outgoing smtp port to 465 and select SSL
- enable Authentication against the outgoing mail server


Internet provider's port 25 is blocked: How to set an alternative port for the SMTP server

If your provider is blocking smtp port 25 on your internet connection but your hosting provider is offering an alternative port (or when using some relay service) you can simply set this alternative port by adding it to the 'Address of Internet provider's mail server' value in the 'E-mail delivery settings' screen of the server-manager like this: 

<internet providers mail server name or ip-address>:<alternative port>

For example: mail.mydomain.com:587

How do I enable and configure a disclaimer in email messages

A disclaimer message can be added to the footer of all outgoing email messages.

The message can be the same for all domains or it can be different for all domains.

This functionality is part of sme7.2 release so make sure you have upgraded before doing this.

To create a general disclaimer for all domains on your sme server 

config setprop smtpd disclaimer enabled
pico -w /service/qpsmtpd/config/disclaimer

Enter the required disclaimer text

To save & exit 

Ctrl o
Ctrl x

To make the changes take effect 

signal-event email-update


To create domain specific disclaimers, create seperate domain based disclaimer text files

Delete the general (all domains) disclaimer file if you have already created it 

rm  /service/qpsmtpd/config/disclaimer
config setprop smtpd disclaimer enabled
pico -w /service/qpsmtpd/config/disclaimer_domain1.com.au
pico -w /service/qpsmtpd/config/disclaimer_domain2.com
pico -w /service/qpsmtpd/config/disclaimer_domain3.org

Enter the required text in each disclaimer file

To save & exit 

Ctrl o
Ctrl x

After making any changes remember to do 

signal-event email-update


Note if you only wish to have a disclaimer for some domains, then only create a disclaimer text file for those domains


Note also the criteria for when a disclaimer is attached

(see http://bugs.contribs.org/show_bug.cgi?id=2648)

eg a disclaimer is added to internal to external messages but not internal to internal messages.

There are also various switches that can be applied

(see http://bugs.contribs.org/show_bug.cgi?id=2648).


To disable the disclaimer function for all domains on your sme server 

config setprop smtpd disclaimer disabled
signal-event email-update


Email WBL server manager panel

There is a server manager contrib to allow GUI control of email white and black lists.

The panel allows easy configuration of functionality that is built into qmail, qpsmtpd and spamassassin. For more information google for qmail & qpsmtpd, read the spamassassin section in this wiki article and see default qpsmtpd plugin confguration).


Warning.png Warning:
It is a test release, although it has been in use since Jan 2007 and appears functionaly stable. To install do: 
wget http://mirror.contribs.org/smeserver/contribs/dmay/smeserver/7.x/testing/smeserver-wbl/smeserver-wbl-0.0.1-a8.dmay.noarch.rpm 
rpm -Uvh smeserver-wbl*.rpm


There are two main sections, Reject and Accept, where you can control settings.

Reject - Black lists are used for rejecting e-mail traffic 

 DNSBL status      - DNSBL is an abbreviation for "DNS blacklist". 
                     It is a list of IP addresses known to be spammers.
 RHSBL status      - RHSBL is an abbreviation for "Right Hand Side Blacklist". 
                     It is a list of domain names known to be spammers.
 qpsmtpd badhelo   - Check a HELO message delivered from a connecting host. 
                     Reject any that appear in badhelo during the 'helo' stage.
 qmail badmailfrom - Check envelope sender addresses. 
                     Reject any that appear (@host or user@host) in badmailfrom during the 'mail'           
                     stage.

Accept - White lists are used for accepting e-mail traffic 

 Whitelists status           - White Lists: ACCEPT
 qpsmtpd whitelisthosts      - Any IP address listed in whitelisthosts will be exempted 
                               from any further validation during the 'connect' stage.
 qpsmtpd whitelisthelo       - Any host that issues a HELO matching an entry in whitelisthelo 
                               will be exempted from further validation during the 'helo' stage.
 qpsmtpd whitelistsenders    - Any envelope sender of a mail (@host or user@host) matching an 
                               entry in whitelistsenders will be exempted from further validation
                               during the 'mail' stage.
 spamassassin whitelist_from - Any envelope sender of a mail (*@host or user@host) matching an 
                               entry in whitelist_from will be exempted from spamassassin rejection.


After making any changes using this panel you must click both the Save and Update buttons, in order for changes to take effect.

External Access

Allow external IMAP mail access

There was a deliberate decision to remove non-SSL protected username/password services from the external interface.

to allow unsecure IMAP access 

config setprop imap access public
signal-event email-update

But before you do this try to use secure IMAP
fixme: explain how

POP3 & webmail HTTP

I want to set my SMESERVER to allow POP3 (or webmail HTTP) but it's not an option, I only see POP3S (or webmail HTTPS).

The SMESERVER is secure by design. POP3 (or webmail HTTP) is viewed as inadequate security and removed as an option from a standard installation to encourage unknowing administrators to select the 'best practice' option -a secure connection with POP3S, IMAPS, or HTTPS.

You can still set your SMESERVER to allow POP3 settings by: 

config setprop pop3 access public
signal-event email-update

Allow external pop3 access

Email settings > POP3 server access in SME 7.1 server-manager allows only pop3s protocol for clients outside the LAN. Some email clients (eg The Bat! v3.98.4) won't allow pop3s connections to SME 7.1 because of ssl version conflict. Until this is sorted out, a workaround is to hack SME to allow regular pop3 on the external interface using the following commands. 

config setprop pop3 access public
signal-event email-update
svc -t /service/pop3s

more information bugzilla:2620

Imap

Folders with a dot in name

Email folder names that have a period ('.') in the folder name, will be split into sub-folders. e.g. folder name 'www.contribs.org' is created as 

www
  contribs
        org

qpsmtpd

SME uses the qpsmtpd smtp daemon.

Official Description

qpsmtpd is a flexible smtpd daemon written in Perl. Apart from the core SMTP features, all functionality is implemented in small "extension plugins" using the easy to use object oriented plugin API.

qpsmtpd was originally written as a drop-in qmail-smtpd replacement, but now it also includes smtp forward, postfix, exim and maildir "backends".

qpsmtpd wiki: http://wiki.qpsmtpd.org


Default Plugin Configuration

SME uses the following qpsmtpd plugins to evaluate each incoming email.

SME maintains 2 distinct configurations: one for the 'local' networks (as defined in server-manager::Security::Local networks) and another for 'remote' networks (everyone else).

The default configuration of each plugin is indicated in the 'Default Status' column.

Plugin Purpose Default Status
hosts_allow Prohibit more than "InstancesPerIP" connections from any single host (change with 'config setprop smtp InstancesPerIP'). Allow or deny connections according to the contents of /var/service/qpsmtpd/config/hosts_allow. See hosts_allow SVN code for more details. upcoming
peers Allow different plugin configuration based on the sending computer's IP address. By default SME maintains different configurations for the local networks (in /var/service/qpsmtpd/config/peers/local) and for everyone else (in /var/service/qpsmtpd/config/peers/0) enabled
logging/logterse Allow greater logging detail using smaller log files enabled
auth/auth_cvm_unix_local Allow authenticated smtp relay enabled (remote)
disabled (local)
check_earlytalker reject email from servers that talk out of turn enabled (remote)
disabled (local)
count_unrecognized_commands reject email from servers that issue X invalid commands enabled (remote)
disabled (local)
bcc bcc all email to a specific address for archiving disabled
check_relay Check to see if relaying is allowed (in case the recipient is not listed in one of SME's local domains) enabled
check_norelay Check to see if the sending server is specifically forbidden to relay through us. enabled
require_resolvable_fromhost Check that the domain listed in the sender's email address is resolvable enabled (remote)
disabled (local)
check_basicheaders reject email that lacks either a From: or Date: header enabled
rhsbl Reject email if the sender's email domain has a reputation for disregarding smtp RFCs. disabled
(always disabled for local connections)
dnsbl Reject email from hosts listed in your configured dnsbl servers disabled
check_badmailfrom Reject email where the sender address is listed in /var/service/qpsmtpd/config/badmailfrom enabled
check_badrcptto_patterns Reject email addressed to any address matching an expression listed in /var/service/qpsmtpd/config/badrcptto_patterns enabled
check_badrcptto Reject email addressed to any address listed in /var/service/qpsmtpd/config/badrcptto enabled
check_spamhelo Reject email from hosts that say 'helo ...' using a value in /var/service/qpsmtpd/config/badhelo enabled
check_smtp_forward If config show DelegateMailServer or db domains show <domainname> MailServer is set (telling SME to deliver email for all domains or just <domainname> to another server), check_smtp_forward will connect to the specified server and will reject the message outright if the internal mail server would also reject it. disabled
unless an internal mail server is configured.
check_goodrcptto Accept email only if the recipient address matches an entry in /var/service/qpsmtpd/config/goodrcptto. For domains that are configured to use an internal mail server, the entire domain name will be added to .../goodrcptto. enabled
rcpt_ok Return 'OK' if none of the other host checks has returned 'DENY' (??) enabled
pattern_filter Reject email according to content patterns (??) disabled
tnef2mime Convert MS TNEF (winmail.dat) and uuencoded attachments to MIME enabled
disclaimer Add a configurable disclaimer to email messages disabled
spamassassin Check email using spamassassin, and optionally reject it completely if the score exceeds a configurable value. disabled
(always disabled for local connections)
virus/clamav Scan incoming email with ClamAV enabled
queue/qmail-queue Deliver the incoming message to qmail for delivery. enabled

Internal Mail Servers

SME can be configured as a spam and antivirus filter for one or more "Internal" mail servers on a domain-by-domain basis. The mail server specified does not have to be on the same local network as your SME server.

Deliver ALL email to a single internal mail server

You can deliver all email for all domains on your SME server to a single internal mail server by setting the mail server address in server-manager::Configuration::E-mail::Change e-mail delivery settings::Address of internal mail server.

Deliver email for one domain to an internal mail server

You can also configure only a single domain to use an internal mail server, or you can configure different domains to use different internal mail servers.

First, create the necessary virtual domains using server-manager::Configuration::Domains::Add Domain.

Then, (assuming your domain is called test.com and the actual mail server is at a.b.c.d issue the following commands: 

db domains setprop test.com MailServer a.b.c.d
signal-event email-update

Secondary/Backup Mail Server Considerations

Many people misunderstand the issues of using a secondary or backup mail server (backup MX) to hold your mail before it gets delivered to your SME Server. If you consider putting a backup mail server in place because you are concerned about lost mail because your internet connection may occasionally drop out, think again and consider the issues discussed below.

What is Backup MX

A backup MX is a system whereby through your DNS records you tell other servers on the internet that in order to deliver mail to your domain they first need to try the primary MX record and if they fail to connect they can try to connect to one or more of your listed backup or secondary mail servers. See also http://en.wikipedia.org/wiki/MX_record

The process of delivering email to your SME Server

So lets look at how mail gets delivered without and with a backup mx when your Internet link, ISP or server is down.

Without a backup MX:
  • The sending mail server cannot connect your server.
  • The sending mail server MUST queue the mail and try again later.
  • The mail stays on the sender's server.
  • The sender's server resends the mail at a later date.

The requirement to re-queue is a fundamental part of the SMTP protocol - it is not optional. So, if your server is offline due to a link or ISP outage, the mail just stays at the sender's server until you are once again reachable.

With a backup MX:
  • The sending mail server cannot contact your server
  • The sending mail server sends the mail to your secondary MX
  • The secondary MX queues the mail until your link/server is up
  • The mail is queued on an untrusted third-party mail server (think about confidential mail between your company and some business partner)
  • The sending mail server's administrator thinks it has been delivered, according to their logs
  • You have no, or little, visibility over the queued mail
  • When your link comes up, the secondary MX sends the mail on to your server
  • You have added more hops, more systems and more delay to the process

If you think that a backup MX will protect against broken mail servers which don't re-queue, you can't. Those servers will drop mail on the floor at random times, for example when their Internet link is down.

Those servers are also highly likely to never try your backup MX.

Thankfully those servers are mostly gone from the Internet, but adding a secondary MX doesn't really improve the chances that they won't drop mail destined for your server on the floor.

Backup MX and SPAM Filtering

On top of the issue, indicated above, there is another issue to consider and that is what happens with SPAM due to the use of a Backup MX.

Your SME Server takes care of filtering a lot of SPAM by checking on the full username & domain at the time it is received.

For example if your server hosts example.com and someone sends mail to joeuser@example.com, the server will only accept the mail if joeuser is a local user/alias/group/pseudonym on the server. Otherwise, the mail is rejected during the SMTP transaction.

A backup mail server however, generally does not have a full list of users against which it can check if it should accept the mail for the given domain. Hence it will accept mail for invalid users.

So:

  • If you trust the secondary MX, you _will_ accept a lot of SPAM when the link comes up.
  • If you don't trust it, you will cause a lot of SPAM backscatter as the mail has been accepted at the secondary MX and then later bounced by you.
  • Stopping backscatter is why SME Server rejects invalid addresses during the initial SMTP transaction.

The SPAM backscatter can only be stopped if the secondary MX has a full list of users for your domain to allow filtering to occur.

But:

  • You need to be able to configure this secondary MX with such user/domain lists
  • You need to maintain these secondary configurations when users are added/deleted from your primary server configuration
  • You need to test (regularly) if the secondary is successfully accepting/rejecting mail as required.

Quite a few sites have lost lots of mail through misconfigured backup MX servers. Unfortunately, the time when you find out they are misconfigured is when you go to use them, and then you find that the backup MX has changed configuration and bounced all of your mail.

Then you realise that this mail could have queued at the sender's site if there hadn't been a broken secondary MX bouncing the mail for you.

  • If you bounce mail at your server, you have logs to show what's wrong.
  • If your secondary MX bounces your mail, you usually have no way to determine what happened other than via reports from the original senders that your mail bounced.

Summary

In summary, if your server/Internet connection is available most (let's say >90%) of the time, you are generally better off without a secondary MX.

If your server/link is down more than this (e.g. dialup), you should not be delivering mail directly to your server.

If you still want to consider setting up a seconday MX, ensure that:

  • you have fully control of the configuration of each of the email gateways for your domain
  • each gateway can make decisions on whether to accept/reject mail for the users at the domain
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