[Dovecot] Server-side sieve for client-side copies

[Eduardo M KALINOWSKI]

Daniel L. Miller escreveu:
> So, without changing the MUA/MTA/IMAP interaction, the IMAP server 
> will simply file new messages according to user-set rules.  Doesn't 
> address the multiple-transfer issue at all, but does provide an option 
> for centralized control of message filing.

With the APPEND command, storing the mail somewhere that is not the 
default location would be a violation of the protocol:

6.3.11. APPEND Command

   Arguments:  mailbox name
               OPTIONAL flag parenthesized list
               OPTIONAL date/time string
               message literal

   Responses:  no specific responses for this command

   Result:     OK - append completed
               NO - append error: can't append to that mailbox, error
                    in flags or date/time or message text
               BAD - command unknown or arguments invalid

      The APPEND command appends the literal argument as a new message
      to the end of the specified destination mailbox.  This argument
      SHOULD be in the format of an [RFC-2822 <http://www.faqs.org/rfcs/rfc2822.html>] message.


The simplest solution would be, as already mentioned, configure the 
client to BCC yourself, and filter that message. (And disable the 'Store 
copy of sent mails' option.) I do not think running filters for 
APPEND'ed messages is an option (even if one not active by default).