Forum Discussion
Exchange Online External OOF
We have a hybrid Exchange 2016/O365 implementation. Whenever a user with a milbox in Exchange Online sets their "Automated Replies" a.k.a. Out Of Office the resulting OOF message end up in the sender...
Check what exactly is causing the messages to be marked as spam by looking at the headers. Might be an SPF fail, or DKIM/DMARC one or something else altogether.