The introduction of email authentication mechanisms like SPF, DKIM, and DMARC have improved email security and spoofing prevention. However, some scenarios have been disrupted by these authentication...
Updated Jul 01, 2019
Version 2.0
Blog Post
Dear Greg Taylor - EXCHANGE,
Thank for your quick reply.
Checking the return path, the SRS seems to work:
testdistributionlist+SRS=TNTem=XF=sending.domain=s.klomp@forwarding.domain
What I do not understand is that even though SRS seems to work, mails from sending.domain sent to a distribution list on our server and delivered to a different mailbox on sending.domain are bounced (by the mail server at sending.domain) due to spf violation. Our spf setting does not give problems if we send a message directly to sending.domain mailboxes, and their spf record should not be relevant due to the SRS.
Looking further down in the mail headers I do notice a second Return Path field showing the actual sender address (no SRS) and the From field remains set to the actual sender address also. Any hints where I can check this: "The SRS feature rewrites the P1 From address (also known as the Envelope From address) for all applicable messages that are sent externally from Office 365"
Anyway, I am afraid to over-ask here and am already happy with the above feedback you gave me and the confirmation that SRS works and something else is causing these problems.
Thanks again!
Sietse