Email address tagging doesn't work with virtual mailboxes in postfix

In /etc/postfix/master.cf configuration file, ensure that the definition of dovecot service, referenced by virtual_transport configuration parameter, is set to suppress the extension part of the recipient address during the call to /usr/lib/dovecot/deliver.

For example, this may not work because ${recipient} will be expanded to [email protected] by Postfix's pipe(8) service:

dovecot   unix  -       n       n       -       -       pipe
  flags=DRhu user=dovecot:dovecot argv=/usr/lib/dovecot/deliver -f ${sender} -d ${recipient}

The ${recipient} macro should be replaced by ${user}@${domain} in this scenario, so that Dovecot delivery agent receives the correct address [email protected] in its command line:

dovecot   unix  -       n       n       -       -       pipe
  flags=DRhu user=dovecot:dovecot argv=/usr/lib/dovecot/deliver -f ${sender} -d ${user}@${domain}

Reference: https://wiki1.dovecot.org/LDA/Postfix