Exchange 2016: 550 5.7.134 RESOLVER.RST.SenderNotAuthenticatedForMailbox
Here's another little problem I stumbled across today. During the migration from Exchange 2010 to Exchange 2016, a user was no longer able to receive emails from external senders (SenderNotAuthenticatedForMailbox) after the spam filters were switched to the Exchange 2016 servers. This problem only occurred when the mail routing was switched to the Exchange 2016 ... Read more