Code:
$ cd /usr/ports/mail/dovecot2
$ make
...
$ sudo make install
===> Installing for dovecot-2.2.4
===> dovecot-2.2.4 depends on shared library: iconv.3 - found
===> Generating temporary packing list
===> Checking if mail/dovecot2 already installed
===> Creating users and/or groups.
Creating group `dovecot' with gid `143'.
Creating group `dovenull' with gid `144'.
Creating user `dovecot' with uid `143'.
pw: user 'dovecot' already exists
*** [create-users-groups] Error code 74
Stop in /usr/ports/mail/dovecot2.
*** [install] Error code 1
Stop in /usr/ports/mail/dovecot2.
[1] 4728 exit 1 sudo make install
$