Dear Community,
we build up a hybrid connection between Exchange 2013 and Office 365.
The wizard went through without issue and also the migration of two users went fine.
But at the moment we have the issue that the migrated users can send from internal to external, but sending from external to internal is not working. There is also no NDR we get etc.
I just saw on the firewall that the mail is blocked due to certification failure. I already searched for the issue, but the used certificate is valid and the only one I can use on the connectors.
Do you have any ideas?