I am having the hardest time tracking down an intermittent problem.
I am running Exchange Server 2003 on a Server 2003 Standard installation which is also the Domain Controller.
Recently, we moved our DNS registration for our domain from Network Solutions to GoDaddy (ostensibly to "consolidate" a number of different domain names). Ever since, we have been receiving intermittent, seemingly random NDR's generated by our server that give the following codes:
The following recipient could not be reached:
USER NAME on 7/9/2009 10:25 am
There was a SMTP communication problem with the recipient's e-mail server. Please contact your system administrator.
<mailserver.mydomain.local #5.5.0 smtp; 553 sorry, that domain isn't in my list of allowed rcpthosts (#5.7.1)>
The user who sent this e-mail (which was a reply with an attachment) sent another e-mail that was new to this same recipient and it went through 2 minutes later. She then sent another reply (at my request) and IT went through, not 10 minutes after that.
I have also been getting these:
The following recipient(s) could not be reached:
USER NAME on 7/6/2009 8:39 AM
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<3dogkcntwolf.ThreeDog.local #5.5.0 smtp;530 authentication required for relay (#5.7.1)>
After the user re-sends this one, it goes as well. So, the problem is intermittent, but it is happening often enough that it is causing serious issues, enterprise-wide.
Any ideas what this could be?