Exchange Online External OOF

Copper Contributor

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 senders Junk Mail folder. This only happens for senders from outside the organization. I've tested this with personal mailboxes in and GMail with the same results. I can't figure out why they would classify these OOF notifications as junk.


Anyone had this problem and if so did you fix it, and if so how ?


Thanks in advance




3 Replies

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.

Hi Robert 


Could you share the header so the I can analyse what is exactly causing the issue. If you can't obviously for privacy reasons try analysing the message header on your end. You could go to and analyse message header there.




Robin Nishad





as pointed out by Vasil, the email header of the OOF message received by external recipients will give you a hint on what's going on.


If you like, you can PM me and I'll sent an email to an OOF enabled mailbox and dig into this further.