I got a lot of pending messages in my message trace, some with 1-2 Receive EVENTs but nothing further. Some with 1 Receive EVENT and then 1 DEFER EVENT with the DETAIL of "The last attempt to deliver the message
encountered an error".
We are using on-premise exchange 2013 and our outbound connectors have Opportunistic TLS set from day 1. Most messages do get delivered fine and theres no common factor in what gets stuck in this state in terms of senders, attachments, subjects or anything
else.
Any ideas?