When people outside your organisation contribute messages to an Exchange distribution group, this can cause DMARC problems that result in mail being bounced.
Your Exchange server will send out the mail from its original sender, but because that sender’s address is in a different domain to yours, the emails sent to distribution group members can be detected as spoofed if the sender’s domain has a DMARC policy.
Our DMARC compliance transport agent solves this problem. It plugs into the Exchange transport pipeline and rewrites the mail sent to distribution groups from outside the organisation so that it comes from the email address of the distribution group itself. This avoids the spoofing issue. It follows the approved approach for address rewriting specified here (section 3A). Mail to distribution group members is only modified if the recipient and the original sender are both outside the organisation.
The DMARC Compliance transport agent is sensitive to the version of Exchange server being used. Currently Exchange 2013 and 2016 are supported. Make sure you install the version that matches your Exchange server.
To install the transport agent, log in to a Mailbox role Exchange server using an account with administrative rights in Exchange and run the .msi file.