It's the never ending mail problem - I see tons of posts about it but none apply. We are all out of ideas.
SMTP queues to verizon, aol, gmail, rightfax, and many others are stuck. All show "the connection was dropped by the remote host"
Verified rDNS/PTR records using www.mxtoolbox.com
; shows OK.
Not an open relay.
HELO address matches rDNS/PTR record
ISP is XO Communications; we do not relay mail over to them (perhaps we should).
No blacklists - did checks using mxtoolbox.
no recent infections of any kind.
Exchange server serves dozens of domains. We got a bunch of users with their own internet domains. So mail comes in on @whateveryouwant.com (example) and goes out the same. The sender address is that of the domain they receive on, not the domain the rdns/ptr is pointed to (should not matter but I want it all on the table).
This problem may have been in and out for a while, but its grown bad.
We have two internal domains, each domain has two exchange servers (total of four). For a while we got around the issue by doing a "problem domain" connector and routing mail for those that bounced through the other server. Well, that stopped working now with the same symptoms. The other exchange server has the same que issue. So now it's an issue because we are out of work-arounds.
Now, mail is still flowing overall, it's just the major domains that are being a problem. We receive and send thousands of emails per day and for the most part there are no delivery issues. It's the users complaining they cant send to AOL that drives me nuts, but we have to resolve it.
Thanks in advance.