On Fri 22 Apr 2016 at 18:29:11 +0100, Lisi Reisz wrote: > On Friday 22 April 2016 18:04:36 The Wanderer wrote: > > I'm talking about what it uses > > for detecting duplicates so it can discard them > > That is worth my while to investigate. I am a bit pushed at the moment, but > will report back.
It's a waste of time. Even if you conclusively demonstrated the offending header was Message-Id: (and it almost certainly is a major player) what would you do? Better is to avoid providers who think it fine to mess with your mail. People wouldn't accept Royal Mail or the US Postal Service doing it. As for duplicates: are the mails sent to the list and the one sent back duplicates? That is, identical in every regard?
