[Dovecot] Shared Mailboxes, Per User SEEN flag and Mailing lists

[Peter Fern]

If all you need is to deliver a single mail to many users at once, you 
might consider hardlinking the message into the mailbox - you may lose a 
little space (never more than one block) as the filename entry in the 
filesystem will require nominal space, but it's likely to be quite 
efficient.  Symlinking won't use any additional filespace for each link, 
but will use inodes... I'm not sure whether dovecot will handle a 
symlink for an actual mail message though - I would assume not.  In any 
case, this will only work properly if you are using maildirs, but then 
if you're not, why not? ;)

Alternatively, the 1.0 series of dovecot does support shared folders, 
and I believe per-user flags are supported, though I'd like someone to 
confirm?  Again, this will only work easily on maildirs due to 
filesystem permissions and such...

Reikan - Sidney Ferreira wrote:

>     Hi!
>     Im making a small research about IMAP servers and it's features. 
> As the subject suggests, I want make a shared mailbox, with per user 
> \seen flag to work like a mailin-list works.
>     The reason to use 1 shared folder is simple: Imagine 12k users 
> sending 1KB messages each week, it will be 12+ MB of useless information.
>     Many people told me that IMAP could do this, but now seem that it 
> is a little harder then what they made it look like.
>     Finally, some EXIM users told me that Dovecot could handle it a 
> little better than Courier, so, Im here to try to find more 
> information about it.
>     Follows the mail that I received from an EXIM user.
>
>         Sidney
>
> Bill Hacker wrote:
> > Reikan - Sidney Ferreira wrote:
> >
> >>     Does Exim works as IMAP?
> >>     Does it allow public folders?
> >>     The SEEN control is made by USER or MESSAGE?
> >>
> >>
> >
> > Exim is an MTA, not an IMAP (or POP) server.
> >
> > It works well with most, perhaps all, POP and IMAP servers.
> >
> > Two widely-used IMAP partners are courier-IMAP and Dovecot.
> > Both of these support POP as well as IMAP.
> > There are several others known to work.
> >
> > Folder sharing can be complex.  IMAP is more appropriate than POP, even
> > if other users are on POP.
> >
> > Exim can use Maildir MBox, and other storage types, can use several at
> > once, can select  the storage location, storage type, UID, GID, and
> > privilege mask from hard-coded, flat-file, db or RDBMS lookup, and can
> > create the storage if it does not already exist.
> >
> > All/any of the above can be done on a per-user, per-domain or 
> per-sender
> > basis, and/or on combinations of the above.
> >
> > The rest is up to the IMAP and client configuration(s).
> >
> > Dovecot can handle Maildir, MBox and other.  Courier-IMAP is optimized
> > for Maildirs.
> >
> > Message state assignments are the responsibility of the retrieval agent
> > (IMAP/POP + MUA).
> > The MTA is not involved once the message has been delivered to storage
> > 9or distant server).
> >
> > As an MTA may process multiple valid messages per valid connection, not
> > all for the same valid user, or even same destination server, Exim does
> > routing and delivery in an area that is essentially per-user OR
> > per-destination sensitive, but always per-message relevant, i.e. -
> > normally handled one at a time at the 'decision making' points.
> >
> > HTH,
> >
> > Bill Hacker