User Databases (userdb)

Dovecot splits all authentication lookups into two categories:

  • passdb and userdb lookup

userdb lookup retrieves post-login information specific to this user. This may include:

  • Mailbox location information

  • Quota limit

  • Overriding settings for the user (almost any setting can be overridden)

Userdb lookups are done by:

Dovecot Director

Dovecot Backend

IMAP & POP3 logins



LMTP mail delivery



doveadm commands



The user database lookup can return these fields:

  • uid: User’s UID (UNIX user ID), overrides the global mail_uid setting.

  • gid: User’s GID (UNIX group ID), overrides the global mail_gid setting.

  • home: User’s home directory, overrides the global mail_home setting. Although not required, it’s highly recommended even for virtual users.

  • Optional extra fields:

  • user: Changes the username (can also be done by the passdb lookup)

  • Overwriting all mail-related settings, for example:

The user and password databases (See Password databases (passdb)) may be the same or they may be different depending on your needs. You can also have multiple databases.

Currently supported user databases are:

  • Passwd: System users (NSS, /etc/passwd, or similar). See Passwd.

  • Passwd-file: /etc/passwd-like file in specified location. See Passwd-file.

  • NSS: Name Service Switch. See NSS.

  • LDAP: Lightweight Directory Access Protocol. See LDAP

  • SQL: SQL database (PostgreSQL, MySQL, SQLite). See SQL

  • Dict: Dict key-value database (Redis, memcached, etc.). See Key-value authentication (dict) database.

  • Static: Userdb information generated from a given template. See Static User Database.

  • VPopMail: External software used to handle virtual domains.

  • Prefetch: This assumes that the passdb already returned also all the required user database information. See Prefetch User Database

  • Lua: Lua script for authentication. See Lua based authentication.

    New in version v2.3.0.

Userdb settings

An example userdb entry might look like this:

userdb {
  driver = passwd-file
  args = username_format=%n /etc/dovecot/users

  default_fields = uid=vmail gid=vmail
  override_fields =

  # v2.2.10+:
  skip = never
  result_failure = continue
  result_internalfail = continue
  result_success = return-ok

  # v2.2.24+:
  auth_verbose = default

First we have the settings that provide content for the userdb lookup:

  • driver: The userdb backend name

  • args: Arguments for the userdb backend. The format of this value depends on the userdb driver. Each one uses different args.

  • default_fields: Userdb fields (and User database extra fields) that are used, unless overwritten by the userdb backend. They are in format key=value key2=value2 .... The values can contain Config Variables. All %variables used here reflect the state BEFORE the userdb lookup.

  • override_fields: Same as default_fields, but instead of providing the default values, these values override what the userdb backend returned. All %variables used here reflect the state AFTER the userdb lookup.

For example useful with userdb passwd for overriding e.g. home directory or the uid or gid. See Passwd.

New in version v2.2.24.

  • auth_verbose: If this is explicitly set to yes or no, it overrides the global auth_verbose setting. (However, auth_debug=yes overrides the auth_verbose setting.)

New in version v2.2.10.

Then we have the setting which specify when the userdb is used:

  • skip: Do we sometimes want to skip over this userdb?

  • never

  • found: Skip if an earlier userdb already found the user

  • notfound: Skip if previous userdbs haven’t yet found the user

And finally we can control what happens when we’re finished with this userdb:

New in version v2.2.10.

  • result_success: What to do if the user was found from the userdb (default: return-ok)

  • result_failure: What to do if the user wasn’t found from the userdb (default: continue)

  • result_internalfail: What to do if the userdb lookup had an internal failure (default: continue). If any of the userdbs had an internal failure and the final userdb also returns continue, the lookup will fail with internal error.


If multiple userdbs are required (results are merged), it’s important to set result_internalfail=return-fail to them, otherwise the userdb lookup could still succeed but not all the intended extra fields are set.

The result values that can be used:

  • return-ok: Return success, don’t continue to the next userdb.

  • return-fail: Return user doesn't exist, don’t continue to the next userdb.

  • return: Return earlier userdb’s success or failure, don’t continue to the next userdb. If this was the first userdb, return user doesn't exist.

  • continue-ok: Set the current user existence state to found, and continue to the next userdb.

  • continue-fail: Set the current user existence state to not found, and continue to the next userdb.

  • continue: Continue to the next userdb without changing the user existence state. The initial state is not found.

Related pages: