What tests is SpamAssassin running? Can I test its configuration?

MIMEDefang runs as the configured defang user, hence, SpamAssassin's integration into MIMEDefang runs as this user, too.

In order to test the configuration use this command (as root):

su defang -s /bin/bash -c 'spamassassin -x -p /etc/mail/sa-mimedefang.cf -D --lint'

• use the correct name for defang you have configured to run MIMEDefang under,
  
• use the correct path for the MIMEDefang-SpamAssassin configuration file /etc/mail/sa-mimedefang.cf
  
• -s /bin/bash ensures that su uses a valid shell, because normally the defang user does not need one
  
• instead of --lint you can pipe or redirect any message to check into this call, e.g.:
  su defang -s /bin/bash -c 'spamassassin -x -p /etc/mail/sa-mimedefang.cf -D' < message
  

Also see: Why don't SpamAssassin DCC/Razor/RBL checks work?