Re: [Fetchmail-users] Duplicate Emails

[Matthias A. <mat...@gm...>]

Am 29.01.21 um 08:59 schrieb Julian Bane:
> Good morning Mattias and all,
>
> I have managed to suppress the X-Original-To header by
> setting*enable_original_recipient = no*" in the postfix configuration
> file. But still don't get duplicate emails suppressed, though the
> X-Original-To header is. (Matthias - I can send you the mailbox file
> if you want).
>
> I have cut out two emails and verified they still have differences in
> the headers (some de-personalization done):
>
>     1,3c1,3
>     < From XXX...@co...  Fri Jan 29 07:38:31 2021
>     < Return-Path: <XXX...@co...>
>     < Delivered-To: up...@my...
>     ---
>     > From jul...@co...  Fri Jan 29 07:38:29 2021
>     > Return-Path: <XXX...@co...>
>     > Delivered-To: do...@my...
>     38c38
>     < X-UID: 24
>     ---
>     > X-UID: 23
>
> It's hard to see how you could ever get two identical sets of headers
> for de-duplication to work.

Julian,

As stated earlier, the deduplication code is from another era, when the
envelope-recording headers such as X-Original-To, Envelope-To,
Delivered-To were not in widespread use, and it was meant as a hack to
avoid local spool explosions when fetchmail resorted to guessing
recipients from the To:/Cc: headers (which breaks with Bcc: quite
obviously) because then it did not have a 1:1 relationship between
server-side message and message-to-ship-onwards.

About X-UID, is it actually transmitted over the wire, or will your
server software suppress it? I guess it goes hand in hand with the
folder-internal status message that is also not sent over the wire.

>
> Not wishing to either make trouble or make work for others but could
> the documentation be reworded to reflect how the de-duplication works.
> Currently it says "/A piece of mail is considered duplicate if it has
> the same message-ID as the message immediately preceding and more than
> one addressee/".

Definitely yes because what you quote is plainly does not refer to what
the code does. I will see to fixing the manual page. I've filed an issue
so I don't forget, because I can't get to it right away. This is 6.4 stuff.

https://gitlab.com/fetchmail/fetchmail/-/issues/29

Best regards,
MNatthias