VPopMail

Dovecot supports authenticating against external VPopMail virtual domain manager. Dovecot must have been configured with --with-vpopmail to enable this. You can check this with dovecot --build-options. See also VMailMgr for another similar virtual domain manager.

If the vpopmail database contains plaintext passwords, it can be used for non-plaintext authentication as well.

passdb parameters:

cache_key: If set, you can use auth_cache with VPopMail. See PAM for more information about it.
webmail=IP: If IP address is specified, connections from it are assumed to come from webmail and VPopMail's webmail usage restrictions apply.

userdb parameters:

cache_key: Like in passdb.
quota_template=TEMPLATE: Template to specify quota rule, %q in value expands to Maildir++ quota.

Example

passdb {
  driver = vpopmail
  args = webmail=127.0.0.1
}
userdb {
  driver = vpopmail
  args = quota_template=quota_rule=*:backend=%q
}

VPopMail + MySQL

Alternatively, you can use the SQL backend with the following configuration:

driver = mysql
connect = host=/var/run/mysqld/mysqld.sock user=vpopmail password=YOURPASSWORDHERE dbname=vpopmail

default_pass_scheme = PLAIN
password_query = SELECT CONCAT(pw_name, '@', pw_domain) AS user, \
  pw_clear_passwd AS password \
  FROM vpopmail \
  WHERE pw_name = '%n' AND pw_domain = '%d'
user_query = SELECT pw_dir as home, \
  89 AS uid, 89 AS gid \
  FROM vpopmail \
  WHERE pw_name = '%n' AND pw_domain = '%d'