We Journal our email to a 3rd party archive company via SMTP rather than a MAPI mailbiox, we have a journal rule configured to send all email to a specific email address email@example.com, we then have a send connector configured to send all email for that email address via a smart host which is mailarchive.3rdparty.com
Today everything stopped working and i ended up with 50'000 emails in the queue for this Smarthost connector.
On troubleshooting i noticed that i could not resolve the FQDN of the smarthost mailarchive.3rdparty.com so thought that must be the issue
However everything kicked back into life and the email queue is going down, heres the twist, even though its now working, from the Hub Transport servers i still cannot resolve mailarchive.3rdparty.com!! so how can this be working??
I turned on verbose logging for the send connector and can see that actually it is making connections to mail.3rdparty.com but i just cant work out how if it cannot resolve the FQDN specified in the send connector how it can possibly get any further.
We have TLS configured for on the send connector and use Basic Authentication over TLS.
Im wondering is there any other way in which this could be resolving