http://faisal.com/docs/salearn.html
Training with Maildir format
Maildir format is a bit different -- it stores each message in a seperate file within one of three subdirectories ('cur', 'new', and...
Try using mailq command to see what the issue is
try this first:service clamav-daemon restart
If the deferred count is way up try this
https://www.howtoforge.com/postfix-amavisd-connect-to-127.0.0....
Postfix spam issues.
Check the queue in /var/spool/postfix the incoming and active directories will have a ton of emails in there if you are under attack.
Step-by-step to check the spools type in te...