Could use some help here. We've been having users complain that their email is either bouncing back to them or they get message delayed emails and finally it bounces back. I checked all the usual things like reversedns, blocklists, etc, but it continues to happen. Currently, if I look in the queue I see a few 421 4.2.1 errors and the message keep retrying. We do have two Interner connections here and the mail could go out on both, but the DNS is set up correctly.
Any help would be appreciated! I also ran the Microsoft Remote connection tests and it passed on both IP's:
Performing Outbound SMTP Test
The outbound SMTP test was successful.
Elapsed Time: 19372 ms.
Attempting reverse DNS lookup for IP address 18.104.22.168.
The Microsoft Connectivity Analyzer successfully resolved IP address 22.214.171.124 via reverse DNS lookup.
Performing Real-Time Black Hole List (RBL) Test
Your IP address wasn't found on any of the block lists selected.
Performing Sender ID validation.
Sender ID validation was performed successfully.
Our mail server would be mail.orbuscompany.com