[Dovecot] How do I use plus-addressing in Dovecot 1.1.x?

[justin at ma3x.net]

Can you post your conf files ? I could try it on one of my setups. I
have no idea how to make + addressing tho >.<

Jon Fullmer wrote:
> I'm using Postfix, Amavisd-new/SpamAssassin, and Dovecot. They all run
> on the same server (running Linux). The mailboxes are stored on the
> same server in maildir format.
>
> The logical path for incoming messages (as I understand it) is:
>
> 1) received by Postfix; handed off to Amavisd-new
> 2) Amavisd-new checks to see whether or not it's spam/undesirable;
> hands off to Dovecot deliver
> 3) Dovecot deliver delivers the message to the local mailbox
>
> Under each of my user's mailbox is a submailbox called "spam". Just so
> I don't confuse terminologies (I'm no IMAP/maildir expert), for
> example, we have someone at domain.com. My configured mail_location is
> "maildir:/srv/mail/%d/%n", so this person's mailbox is located here: 
> /srv/mail/domain.com/someone/   Within this directory is another
> mailbox:  /srv/mail/domain.com/someone/.spam/
>
> The plan is to have Dovecot deliver send a message (which has been
> labeled by Amavisd-new as spam) directly to the ".spam" submailbox,
> instead of the INBOX (/srv/mail/domain.com/someone/). With Dovecot
> 1.0.x, I used "plus addressing". Amavisd-new was configured so that,
> if a message was found to be spam, it delivered the message to Dovecot
> deliver, but changed the delivery address. Now, instead of
> "someone at domain.com", it was "someone+spam at domain.com". Dovecot
> deliver took this message and delivered it correctly to the ".spam"
> submailbox (/srv/mail/domain.com/someone/.spam/). Just to emphasize,
> this process does work (using Dovecot 1.0.x).
>
> With Dovecot 1.1.0, this process is broken. Now, spam messages are
> delivered to the INBOX instead, and, when checking the
> dovecot-deliver.log, I'm seeing "save failed to spam: Unknown namespace".
>
> As best as I can tell, the answer seems to lie in "namespaces" as a
> feature added in Dovecot 1.1.0. The problem is that I don't understand
> how I could use them to resolve this situation. I've read the
> documentation. I've looked at as many example configurations as I
> could find.
>
> Please help. I want to get this working again. I'm sure it's something
> very straight-forward, but I don't understand. How must I change my
> Dovecot 1.1.x configuration so that my "plus addressing" set up
> (detailed above) will work again?
>
> Or is there a better way?
>
> Thanks so much for your help, and thanks for a great product!
>
>  - Jon