[Dovecot] recipient delimiters and virtual users

[Nick Edwards]

Is there a known workaround for users who want to use the old recipient
delimiter plus sign method of sorting their mail? eg:  foo.bat
+dove...@example.com <foe.blow%2bdove...@example.com>

This does not work with postfix/dovecot, but if we tell
postfix/system-passwd to use the recipient_delimiter = +  it works just like
I recall sendmail did, but we no longer use local users only  virtual
dovecot LDA w/mysql.

postfix appears to accept it testing by telnet, but then the message gets a
new DSN generated saying no user, so
  dovecot LDA must not work by default with this.

Postfix 2.8.3
Dovecot 1.2.17
MySQL 5.5.12


our postfix master.cf is
dovecot   unix  -       n       n       -       -       pipe
   flags=DRhu user=mail:mail argv=/usr/libexec/dovecot/deliver -e -d
${recipient}