We're having non-stop issues with forwarded mail on our cPanel server, customers complaining furiously that their emails don't seem to be getting through.
Many of these users have an email@example.com email address which is set up as a forwarder to their AOL, Yahoo or Hotmail account. Sporadically, some legitimate messages don't arrive in their inbox.
Our current theory is that AOL, Yahoo and Hotmail are essentially "shooting the messenger" - these people receive quite a bit of spam which our server is diligently forwarding to their @aol.com, @hotmail.com or @yahoo.com email addresses. Because this mail is coming from our server, our messages get silently discarded after a while. The messages do not end up in the user's Spam folder, they get discarded entirely.
Is there anything we can do about this?