Let me explain the issue because there are two of them (we think).
We have three exchange servers.
A. Exchange 2007 (in a WS2008 AD)
B. Exchange 2013 (in a WS2012 AD)
C. Exchange 2019 (in a WS2019 AD)
There are several domain names on server B, but only one domain that is shared between all three servers.
For over a year, A and B shared a domain, then C was installed this year (two weeks ago).
None of the servers are in the same AD.
External mail for the sharedomain.com comes to B.
If it gets mail for users that aren't on B it relays to A.
When someone on A sends e-mail to a user not on A it gets relayed to B.
Once C was introduced, C was told to forward to B, B still to A, and A changed to forward to C.
It was working for a couple of days then stopped.
Also, server C will not send any e-mail at all, even though the logs say e-mail is being handed off.
Even Hotmail is not receiving e-mail from server C.
Also we're assuming that B stopped receiving from C but can't show it.
Any help is appreciated.
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