[Dovecot] Keywords (labels) support via virtual folders

[Robert Tomanek]

Hi all,

 while I am rather a beginner when it comes to IMAP, I was thinking
 whether it would be possible (and feasible) to implement setting and
 unsetting of IMAP keywords with the means of virtual folders in
 Dovecot. 

 The background is that the IMAP keywords seem to be a very useful
 thing to me: I would often like to be able to 'tag' a message so that
 it is easy to group with other similar messages and easy to find/
 browse later. The problem is that not all IMAP clients support this
 functionality (as far as I am aware, mine which happens to be The
 Bat! does not); the only way of achieving similar results is using
 regular folders for grouping messages but this has several
 disadvantages, the most prominent one being unable to assign more
 than one 'tag' to a message this way (without copying a message).

 What I am thinking of is a server-side 'helper' that intends to
 achieve functionality similar to native client keywords support by
 the means of providing 'virtual folders' (as opposed to regular
 folders that we've known for a long time).
 The server would expose a list of virtual folders (user defined,
 either server-side by modifying the configuration, or client-side,
 by using the existing 'create regular folder' folder functionality
 but using a special name format that would be recognized by the
 server to be virtual folder related). These virtual folders would,
 upon moving a message to them, apply a keyword to the message (but
 the message would not be moved as it would be the case with regular
 folders). Upon moving a message from a virtual folder, the keyword
 would be reset.
 This means that the messages would not normally be moved from their
 place in existing hard folder structure but they would additionally
 be flagged with a keyword (or more of them) and be visible in
 respective virtual folders.

 The result is:
 - keywords support for clients that do not natively support it,
 - leaving existing message folder structure intact,
 - support for multiple keywords/ labels per message (one virtual
   folder = one keyword),
 - browsing flagged messages via respective virtual folders.

 What do you think of it?

 While I've been toying with this and similar ideas for a long time,
 what I propose above is of course heavily influenced by the recent
 addition of IMAP access to Gmail ([1]). While I still do not have it
 enabled for my account, I presume this is how the Gmail labels get
 translated to IMAP client ([2], [3]).

 [1] https://mail.google.com/support/bin/topic.py?topic=12760
 [2] https://mail.google.com/support/bin/answer.py?answer=77657&topic=12762
 [3] https://mail.google.com/support/bin/answer.py?answer=78758&topic=12762
 
-- 
Best regards,
 Robert Tomanek              mailto:dovecot at mail.robert.tomanek.org