Date: Tue, 15 Dec 2009 19:54:11 -0500
From: Alec Berryman <alec@thened.net>
To: David Bremner <david@tethera.net>
Message-ID: <20091216005411.GA28199@thened.net>
References: <87pr6gcuiu.fsf@pivot.cs.unb.ca>
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User-Agent: Mutt/1.5.20 (2009-06-14)
Cc: notmuch@notmuchmail.org
Subject: Re: [notmuch] notmuch and imap [musing, no code :)]
Precedence: list

David Bremner on 2009-12-15 08:05:13 -0400:

> Recent discussions on IRC (I forget with whom, sorry), brought me back
> to thinking about syncing notmuch with imap.  In addition to the flags
> \Seen, \Answered, \Draft, \Deleted, and \Flagged, imap servers can
> optionally support user defined keywords (i.e. tags). At least courier
> and dovecot do.  These keywords are imap "atoms", which, without tracing
> though the BNF [1] completely look like they can can have (ascii)
> alphanumeric, and punctuation other than brackets, quotes and "%", "*".

I am also very interested in syncing tags between computers.  I started
implementing storage of tags in message headers.  It's has been done
before - several mutt extensions and systems use X-Label.  This approach
offers several advantages to notmuch dump/restore and IMAP flags:

  - compatability: most mail clients can search on headers, so even if
    you're not using notmuch full-time (squirrelmail? phone?), you can
    get some benefit from it

  - works with offlineimap without further effort: no new transport
    mechanism required

  - a migration path: text-based mail sorting tools like procmail can
    easily set headers

  - backups are easy: you can't miss backing up your tags because
    they're in the messages

There are security concerns (need to strip incoming messages of tags so
no one tags your mail for you), privacy concerns (if you forward the
entire message as an attachment, may want to strip tags), and space
concerns (how many flags?), but I think they can be worked around.

I haven't gotten very far with my implementation due to time
constraints.  It reads tags fine, but I haven't implemented writing,
which is the involved part.  I hope to get to this between Christmas and
New Years, but who knows.