[Dovecot] New deduplicate doveadm command - was Re: v2.2.4 released

Ralf Hildebrandt Ralf.Hildebrandt at charite.de
Tue Jun 25 17:04:12 EEST 2013

* Reindl Harald <h.reindl at thelounge.net>:
> Am 25.06.2013 15:28, schrieb Timo Sirainen:
> > Also there are several potential problems.. Like if there are duplicate Message-ID: headers, 
> > but the body is different, should that be a duplicate?
> the answer is simply *yes* because there must not be the same
> Message-ID's for different messages because the words "single
> unique message identifier" are pretty clear
> _______________________________________________________
> RFC2822
>    Though optional, every message SHOULD have a "Message-ID:" field.
>    Furthermore, reply messages SHOULD have "In-Reply-To:" and
>    "References:" fields as appropriate, as described below.
>    The "Message-ID:" field contains a single unique message identifier.
>    The "References:" and "In-Reply-To:" field each contain one or more
>    unique message identifiers, optionally separated by CFWS.
> _______________________________________________________
> these days "every message SHOULD have a Message-ID:" is outdated
> we started many years ago to block *any* message missing the
> header because every sane SMTP implementation adds it if it
> was missing from the client and so only broken implementations
> which are mostly spammers would be affected

We had one funny occurance of that particular corner-case:

* Somebody sent us an email
* the user's account autoreplied on the eveing upon receipt (out of office)
  That autoreply was sent with a message-id A
* next morning, the user read the mail, and composed a personal reply  
* that reply was discarded by the recipient's mailserver, since it had the same message-id A (dunno why that happened, but it did!)
  as the auto-reply the evening before.
That took me a while to discover.  

Ralf Hildebrandt
  Geschäftsbereich IT | Abteilung Netzwerk
  Charité - Universitätsmedizin Berlin
  Campus Benjamin Franklin
  Hindenburgdamm 30 | D-12203 Berlin
  Tel. +49 30 450 570 155 | Fax: +49 30 450 570 962
  ralf.hildebrandt at charite.de | http://www.charite.de

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