[Dovecot] IMAP threading - the THREAD command

[Timo Sirainen]

On Fri, 2006-04-07 at 15:50 +0200, Jan Kundrát wrote:
> The second method is actually advertised and supported by Dovecot.
> However, I've got quite a lot of friends that lack the knowledge of what
> the "Subject" field is for, so they just leave it empty. The problem
> comes when I want Dovecot to return the threads - it follows the ietf
> draft, so it doesn't check only for references from message headers, but
> also the subjects. The result is that especially those mails with empty
> subjects are incorrectly grouped together.

I don't really like that either. I don't have the problem with empty
subjects, but the same generic subjects are used by different people
once in a while, such as "Dovecot".

> a) Don't look at the Subject field at all - altough it might increase
> the speead a bit, it has some disadvantages as well, namely that you'll
> lose threading if someone uses broken mail client (but broken only in
> such a way that it preserves subjects)
> 
> b) Ignore the Subject field if it is empty (after stripping stuff like
> "re:" etc - just as that draft specifies). Seems reasonable, IMHO.

I've been thinking about adding some time limits, like the subjects are
grouped only if their date difference is less than, say, 3 days.

> Of course we can't modify the result of a THREAD command (that would
> break the standard and it generally isn't a proper way to go), so we'd
> have to introduce another one.

THREAD=REFERENCES2 or something. :)

> I'm pretty sure that especially method a) is very simple (and even
> simpler if I decided to break the standard by "fixing" the THREAD
> command), 

b) is probably easier since the subject merging is done only after
removing the Re:, etc.

> but I really don't like <rant>portable assembler :)</rant>
> <politely>C</politely>, so are there any chances for this "new and
> fixed" command to be included into Dovecot? I mean, I might do that in a
> flawed and ugly way just for me and post a patch so that possible
> interested persons can pick it, or I migth persuade someone to do it,
> actually :). Do you think that it's worth the issue?

While at it I think another thing that needs fixing is that threads
should be sorted by their latest mail's received-date, not the first
mail's date-header.

If others agree with this, the REFERENCES2 algorithm could do both of
these.

> Does anyone have any experiences with talking to the IETF about possible
> extension of their draft?

I don't think that draft can be updated much anymore. Instead a
completly new draft could be made which depends on it.. I was just
talking about this in imap-proto list a few days ago.
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