[sdiy] [ADMIN] Forwarding of messages

[Ben Stuyts]

Hi all,

TLDR: Don’t forward you list emails to another domain.

As you probably know, every now and then we see complaints of a few list members not receiving all messages. They are visible in the mailing list archive, and also received by most other people.

Thanks to Mattias and Mike, I think I might have found at least one probably cause for this: Forwarding from one domain to another. For example:

- list member is subscribed as person at example.org <mailto:person at example.org>.
- email from list is sent to example.org <http://example.org/> mail server.
- example.org <http://example.org/> forwards this mail automatically to person at gmail.com <mailto:person at gmail.com>.
- google receives this email from example.org <http://example.org/> but sender is still: synth-diy at synth-diy.org <mailto:synth-diy at synth-diy.org>.
- google checks SPF record (an anti-spoof measure) for synth-diy and sees that only the mail server for synth-diy.org <http://synth-diy.org/> is allowed to do this.
- google refuses the mail and bounces it back, mail is ‘lost’ to person at gmail.org <mailto:person at gmail.org>.

This problem was elusive to me in the past because bounce message were not saved at my end. They now are, and I got a better picture of this.

Note that this problem is not limited to this (or any other) mailing list. It can (and did) also happen with private emails. In Mattias’ case, this was what got me on track.

So, hope this helps.

Ben