dovecot - Oct 2008 - Feature wish: "Virtual" POP3 folder with IMAP

Hallo,

is it possible to implement a "flat folder view" for POP3 users?  

The problem is that POP3 only knows one folder: INBOX.  Now, if a user logs
in via POP3, he won't see messages that live outside the INBOX folder - this
could be e.g. a *SPAM*-flagged message moved to another folder via
Sieve/LDA/other mechanism.

What about adding a feature `pop3_remap_folders` to virtually place *all*
messages spread across different folders inside INBOX, only for the POP3
session, and without impact on the actual folder structure as seen thru
IMAP?

I see some issues though:

	- How would SENT and TRASH be handled?  These special folders
shouldn't be part of the game.

	- What happens if the POP3 client deletes a message, which is the
default behavior of Outlook and friends?  Proposed logic: really delete
message if not logged in via IMAP since ($filemtime_of_message -
$user_configurable_amount_of_seconds), else gracefully ignore client's
delete request.  This *could* become a problem if quotas are enabled, but
then again it should be the admin's decision to offer this feature to his
users.

	- Message IDs: Would the above Delete-only-if workaround confuse
some mail clients and make them download the same messages over and over?

	- Perhaps another way: create a separate POP3 directory inside the
mailbox, only used by dovecot-pop3.  Inside reside symlinks to the actual
messages spread across different IMAP folders, which can safely be deleted
by a POP3 client and also following the real-delete logic described above.

The benefit of such a virtual folder remapping would be great for systems
also using webmail and/or Sieve.

Regards,
James

--
jbdovecot at fcgh.net

on 10-3-2008 11:44 AM jbdovecot at fcgh.net spake the
following:
> Hallo,
> 
> is it possible to implement a "flat folder view" for POP3 users?
> 
> The problem is that POP3 only knows one folder: INBOX.  Now, if a user logs
> in via POP3, he won't see messages that live outside the INBOX folder -
this
> could be e.g. a *SPAM*-flagged message moved to another folder via
> Sieve/LDA/other mechanism.
> 
> What about adding a feature `pop3_remap_folders` to virtually place *all*
> messages spread across different folders inside INBOX, only for the POP3
> session, and without impact on the actual folder structure as seen thru
> IMAP?
> 
> I see some issues though:
> 
> 	- How would SENT and TRASH be handled?  These special folders
> shouldn't be part of the game.
> 
> 	- What happens if the POP3 client deletes a message, which is the
> default behavior of Outlook and friends?  Proposed logic: really delete
> message if not logged in via IMAP since ($filemtime_of_message -
> $user_configurable_amount_of_seconds), else gracefully ignore client's
> delete request.  This *could* become a problem if quotas are enabled, but
> then again it should be the admin's decision to offer this feature to
his
> users.
> 
> 	- Message IDs: Would the above Delete-only-if workaround confuse
> some mail clients and make them download the same messages over and over?
> 
> 	- Perhaps another way: create a separate POP3 directory inside the
> mailbox, only used by dovecot-pop3.  Inside reside symlinks to the actual
> messages spread across different IMAP folders, which can safely be deleted
> by a POP3 client and also following the real-delete logic described above.
> 
> The benefit of such a virtual folder remapping would be great for systems
> also using webmail and/or Sieve.
> 
A pop3 user probably wouldn't be using any server side filtering. If you
have
mostly pop3 users you should be just adding headers or modifying the subject
so they can client side filter them.

I don't think there should be any default server side filtering except for
either tagging or deleting said flotsam. A user should be technically able to
know how and what the filters are and how to use them, and be using IMAP if he
wants server side filtering that moves mail around.

Besides what you propose probably violates a few RFC's.

-- 
MailScanner is like deodorant...
You hope everybody uses it, and
you notice quickly if they don't!!!!

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James wrote:
> is it possible to implement a "flat folder view" for POP3 users?
No. If you need folder, use IMAP. If you need Sieve, use IMAP. If you need
Sent or Spam folders, use IMAP.

POP3 is limited and it is neither possible nor useful to simulate IMAP
behavoir with POP3. That's the reason why IMAP was invented.

Heiko

Heiko Schlichting          Freie Universit?t Berlin
heiko at FU-Berlin.DE         Zentraleinrichtung f?r Datenverarbeitung (ZEDAT)
Telefon +49 30 838-54327   Fabeckstra?e 32
Telefax +49 30 838454327   14195 Berlin

On Fri, 2008-10-03 at 20:44 +0200, jbdovecot at fcgh.net
wrote:
> is it possible to implement a "flat folder view" for POP3 users?
v1.2 has virtual mailboxes where you could create a virtual INBOX for
POP3 users.
> 	- What happens if the POP3 client deletes a message, which is the
> default behavior of Outlook and friends?  Proposed logic: really delete
> message if not logged in via IMAP since ($filemtime_of_message -
> $user_configurable_amount_of_seconds), else gracefully ignore client's
> delete request.  This *could* become a problem if quotas are enabled, but
> then again it should be the admin's decision to offer this feature to
his
> users.
> 
> 	- Message IDs: Would the above Delete-only-if workaround confuse
> some mail clients and make them download the same messages over and over?
Probably.

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