Re: Mailing list usage questions

[Jeffrey Walton <noloader@gmail.com>]

On Wed, Apr 12, 2023 at 1:52 PM <tomas@tuxteam.de> wrote:
>
> On Wed, Apr 12, 2023 at 12:38:37PM -0400, Jeffrey Walton wrote:
> > On Tue, Apr 11, 2023 at 10:12 PM The Wanderer <wanderer@fastmail.fm> wrote:
> > >
> > > ...
> > > Some mail services apparently treat this "discard incoming messages that
> > > look like duplicates of ones you already have a copy of" behavior as a
> > > feature; Gmail is the best-known example. That has problems when (as
> > > with this mailing list) the incoming copy is not identical to the one
> > > that was sent, even though it has the same Message-ID, but AFAIK they
> > > don't seem to care.
> >
> > I believe Message-Id's are supposed to be unique across space and
> > time. It sounds like discarding the duplicate is expected behavior (to
> > me).
>
> Still it doesn't make much sense discarding incoming messages which
> match the IDs of outgoing ones.

Most (nearly all?) mail agents follow the RFCs. The RFCs say a
Message-Id is unique across space and time. A duplicate Message-Id
means a duplicate message.

If you wish to wander from the convention, then don't be surprised
when unexpected things happen.

Jeff