we have a problem with one exchange server (SBS2011)
Everything works fine, but the server cannot send emails to some domains.
- The domains have - according to them - whitelisted us in their antispam
- The domains apparently don't see anything in their logs about our server trying to send
- reverse-lookup has been added to our server, but no help
The server has tried to deliver this message, without success, and has stopped trying.
#550 4.4.7 QUEUE.Expired; message expired ##