PMG + Exchange 2019 - out of office reply (SPF + DMARC reject policy)


Jul 10, 2019
We have an internal Exchange Server which receives an sends mails through pmg. LDAP is not set up, so its only a gateway.
All is working as expected so far.

We have an DMARC and an SPF entry setup which tells to reject non conform mail senders.

Here comes the problem, were I want to find a workaround;
If a Mailbox puts in an out of office message, the mail gets bounced by some receivers (eg. google) because of:

550-5.7.26 Unauthenticated email from is not accepted due to domain's 550-5.7.26 DMARC policy.

I understand that Exchange puts in an empty sender into the "out of office" message. On Outlook there is a sender so I guess there is a second header (return-path, envelope?) which includes the correct mail sender adress.

Whould it be possible to add the missing sender header with a proxmox rule without "cringing" around with exchange?
Does anyone found already a working solution for this?

Thanks for our Advices.


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