I currently only allow connections on port 25 from a mail filtering service's IPs.
I have Exim running on an alternate port for SMTP submission. This port needs to allow non-encrypted connections for now so I can't rely on forcing TLS on the port.
I would like to configure Exim to drop non-authenticated SMTP connections on the alternate port to prevent spammers from connecting and sending spam directly to users.
How would I configure this ACL?