Configuring Sieve & Submission

postmaster_address

postmaster_address = postmaster@%{user | domain}

Email address to use in the From: field for outgoing email rejections.

The %{user | domain} variable expands to the recipient domain.

Domain (%{user | domain}) is Empty

IMAP or POP3 protocol doesn't have explicit support for domains. The usernames are commonly in user@domain format, and that is also where Dovecot gets the domain from. If the username doesn't have @domain, then the domain is also usually empty (unless auth_default_domain is used).

If you login as user@domain, but the %{user | domain} is still empty, the problem is that your configuration lost the domain part by changing the username. Dovecot doesn't keep track of the domain separately from username, so if something changes username from user@domain to just plain user, the domain is lost and %{user | domain} returns nothing. If you have auth_debug = yes, this shows up in logs like: Info: auth(user@domain.org): username changed user@domain.org -> user.

Below are some of the most common reasons for this.

Settings

auth_username_format changes the username permanently when used globally. If used inside passdb or userdb, it changes the username only for the duration of the lookup. See also Virtual and System Users.

SQL

passdb_sql_query gets often misconfigured to drop the domain if username and domain are stored separately. For example:

# BROKEN:
passdb sql {
  query = SELECT username AS user, password \
    FROM users \
    WHERE username = '%{user | username}' AND domain = '%{user | domain}'
}

The "username AS user" changes the username permanently and the domain is dropped. You can instead use:

# MySQL:
passdb sql {
  query = SELECT concat(username, '@', domain) AS user, password \
    FROM users \
    WHERE username = '%{user | username}' AND domain = '%{user | domain}'
}

Or you can return username and domain fields separately and Dovecot will merge them into a single user field:

passdb sql {
  query = SELECT username, domain, password \
    FROM users \
    WHERE username = '%{user | username}' AND domain = '%{user | domain}'
}

submission_host

submission_host = smtp-out.example.com:25

SMTP server which is used for sending email rejects, Sieve forwards, vacations, etc.

Alternatively, sendmail_path setting can be used to send mails using the sendmail binary.