Sieve and SMTP submission

postmaster_address = postmaster@%d

Email address to use in the From: field for outgoing email rejections. The %d variable expands to the recipient domain.

See Domain (%d) is empty details when this does not work.

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.

protocol lmtp {
  mail_plugins = $mail_plugins sieve
}