[Dovecot] Envelope From changed - why?

[Miquel van Smoorenburg]

On 2004.04.27 09:53, Tom Alsberg wrote:
> Comment below:
> 
> On Mon, Apr 26, 2004 at 11:43:59AM +0200, Miquel van Smoorenburg wrote:
> > On 2004.04.26 09:03, Tom Alsberg wrote:
> > ><snip />
> > > However, the mbox format does store those lines, and they even still
> > > have some meaning.
> > 
> > Why not let your MDA or local delivery agent add a proper Return-Path:
> > header. It contains the same information as the From_ line, but it works
> > with all mailbox types, it's easier to parse and you can get at it using IMAP.
> 
> Well, my MTA, as most others, does add a Return-Path: header.  Usually
> it contains the same information as the From_ line, but not always, 

I think that would be a bug.

> IIRC (the Return-Path: header, IIRC, may be altered/added to by an 
> SMTP relay in the way

No, the Return-Path header is not present at SMTP transport time. It is
added the moment the message leaves the SMTP domain, i.e. the moment it
drops into a local mbox (or is sent through another transport like UUCP).
That is the same moment a From_ header is added, and the content should
be the same.

> while the envelope From_ line is guaranteed to
> remain as it was).

The From_ line is only retained over UUCP, no other transport has a
From_ line in the message. SMTP certainly doesn't.

> Never mind that, however - naturally I can have 
> the same information stored also in the headers (X-Envelope-From: or
> something like that).
> 
> However, I would still like the From_ line to remain intact - I see no
> reason to rewrite it while copying the message, instead of keeping the
> original one.  Actually, some user agents and other software even do 
> read it and regard it (for filtering, marking messages, sorting and 
> merging mailboxes, etc.), so it disturbs a bit when that's changed.

Well, when COPYing mailboxes over IMAP dovecot should be able to retain
the From_ line I suppose (if the internal API is rich enough) - but if
the MUA does something like get message from folder A and write it
to folder B (which many clients still do) the From_ line gets lost.

I suppose the mbox folder code could get the basic info for the From_ line
from the Return-Path: header if it is present. That's what my own mbox
library for internal projects does...

Mike.