we have an Exchange issue regarding the email receiving from specific "3" domains. Those domain users can receive our emails but they can't send emails to our domain, even they didn't receive any NDR.

we check our edge servers and the emails land on both edge servers, but one edge server can't deliver to the mailboxes. I run the edge sync and after that we start receiving emails from those domains.

We've not seen any error / warning logs on Edge server. The same edge server is receiving emails from other domains and delivering to end user mailbox without any issue. Anyone has seen this issue? and know why it happens?

Pls note that we're using Exchange 2013 CU5 in our production.

Hi

Can you update to CU8 or CU9 and see if the problems resolves?

The last 2 CU's have alot of fixes in them?