Add mail server setup scripting.

[config] / buster / etc_files / mail / etc / dovecot / conf.d / 99-lmtp-sieve-filtering.conf

# This is only necessary when we use dovecot's LMTP mechanism to receive
# mail from postfix.
auth_username_format = %Ln

# Add sieve filtering.
protocol lmtp {
  mail_plugins = $mail_plugins sieve
}

# We don't strictly need to provide a LMTP server to fetch mail from
# postfix, but we do if we want to do sophisticated stuff like sieve
# filtering on the way.
service lmtp {
  inet_listener lmtp {
    address = 127.0.0.1
    port = 2424
  }
}