Q: Mail Server does not always send
I have a vexing problem for our small business Mac OS X server.
The server essentially has only 3 users using the mail server. One user sends 10x more email than the others and is of course the person with this problem. The problem being that his outgoing emails do not always get sent, or more accurately, not always accepted by the receiving mail server. The most maddening problem is that he may not get the returned error message for 4 days. This certainly does not happen with all sent emails, maybe 10%. Mail is not relayed through the local ISP.
Most of the error codes received are complete gibberish to me but the last one said,
Diagnostic-Code: smtp; 550 5.7.1 Sorry, message looks like spam or phish to me
(OP)
As best as I can tell, some of the receiving mail servers just do not like the OS X server mail server. Other emails sent at nearly the same time to non problematic mail addresses work fine. For instance, he can always send to my iCloud email address.
Therefore, I know internet connectivity is good. The server has a static ip address and is behind an older airport extreme router. The server does a lot of things, but again serves a very small number of people; mail, file, print, vpn, contacts, profile manager, time machine, caching, calendar, dns.
All current updates, etc. have been installed.
I would appreciate any diagnostic pointers or help.
Mac Pro, OS X Server, 2.66 quad core xeon 18gb
Posted on Apr 9, 2016 2:55 PM