The default DKIM key is created in /home/e-smith/dkim_keys/default. To enable DKIM signing for all the domains that you manage:
+
db configuration setprop qpsmtpd DKIMSigning enabled signal-event email-update
+
If you want to disable dkim signing for a domain, you can use:
+
db domains setprop domain.com DKIMSigning disabled
+
signal-event email-update
+
The default behavior is to use the same key pair for all your domains. But you can create other key pairs for specific domain if you want. For example, if you want to use a specific key pair for the domain.net domain:
+
cd /home/e-smith/dkim_keys
+
mkdir domain.net
+
cd domain.net
+
echo default > selector
+
openssl genrsa -out private 2048
+
openssl rsa -in private -out public -pubout
+
chown qpsmtpd:qpsmtpd private
+
chmod 400 private
+
signal-event email-update
+
Now, the emails using a domain.net sender address will be signed by this new key instead of the default one.