Pigeonhole redirect is adding a message-id header when it already exists

Sat Oct 1 11:45:56 UTC 2022

>Oct  1 13:31:46 xxxx sendmail[30321]: 291BVjjx030318: to=<xxxx at gmail.com>, delay=00:00:01, xdelay=00:00:01, mailer=esmtp, pri=122536, relay=gmail-smtp-in.l.google.com. [142.250.102.27], dsn=2.0.0, stat=Sent (OK  1664623906 gs19-20020a1709072d1300b00777a40d515dsi4096082ejc.456 - gsmtp)
>
>I just tested for you, enabled the sieve forward, send test mail and the forward is being accepted by google.
>
>

It looks to me you're dismissing the fact that it only concerns the 
forwarding of mails that have originally a "bogus" Message-ID.

That's the only way to trigger the issue. Other mails (that are missing 
Message-ID or having RFC compliant Message-ID are forwarded and accepted 
just fine by gmail :)