When any account @domainA.com sends to a specific address (eg. b@domainB.com) it bounces. When they send to another address at the same account (eg. c@domainB.com) it goes through just fine. c@domainB.com has existed for a number of years now, b@domainB.com is relatively new, and has had this issue since created.
b@domainB.com can receive emails from any other domain, just not domainA.com.
I set up a forward address (call it d@domainB.com) which passes the email on to b@domainB.com as well as my work account which is on another domain. When a@domainA.com sends to d@domainB.com, I receive the forwarded email, but b@domainB.com does not.
My questions.. More generally, what in the world is happening here? Specifically, is this issue something on the receiving end or the sending end? and how do I fix it if it's on the receiving end (which I control) or what do I tell the guys on the sending end to look for?
Here is the message received by domainA.com users when they send to the account:
Your message did not reach some or all of the intended recipients. Subject: Test Sent: 1/29/2010 8:25 AM The following recipient(s) cannot be reached: 'b@domainB.com' on 1/29/2010 8:25 AM 550 unknown user