On Wed, Apr 12, 2023 at 1:52 PM <[email protected]> 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 <[email protected]> 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
