We will allow users to categorize mail as Spam by placing them in user-specific Spam mailboxes. Contrary moving a message flagged as Spam to any other mailbox will relearn it as Ham.

IMAPSieve configuration

Dovecot supports this via its IMAPSieve plugin which we will configure in our custom configuration /etc/dovecot/local.conf to avoid touching release-specific files in /etc/dovecot/conf.d/.

# 90-sieve.conf:
# ----------------------------------------------------------------------
# Messages can be marked as SPAM or HAM by moving them between mailboxes

plugin {
  sieve_global_dir = /var/vmail/conf.d/%d/sieve
  sieve_global_extensions = +vnd.dovecot.pipe +vnd.dovecot.execute
  sieve_plugins = sieve_imapsieve sieve_extprograms

  # From elsehwhere to Spam folder
  imapsieve_mailbox1_name = Spam
  imapsieve_mailbox1_causes = COPY
  imapsieve_mailbox1_before = file:/var/vmail/conf.d/rspamd/report-spam.sieve

  # From Spam folder to elsewhere
  imapsieve_mailbox2_name = *
  imapsieve_mailbox2_from = Spam
  imapsieve_mailbox2_causes = COPY
  imapsieve_mailbox2_before = file:/var/vmail/conf.d/rspamd/report-ham.sieve
}

# 90-sieve-extprograms.conf:
# ----------------------------------------------------------------------

plugin {
  sieve_pipe_bin_dir = /var/vmail/conf.d/rspamd
}

Learning scripts

The following scripts will be stored in /var/vmail/conf.d/rspamd/ and will interact with Rspamd.

/var/vmail/conf.d/rspamd/report-ham.sieve

require ["vnd.dovecot.pipe", "copy", "imapsieve", "environment", "variables"];

if environment :matches "imap.mailbox" "*" {
set "mailbox" "${1}";
}

if string "${mailbox}" "Trash" {
stop;
}

pipe :copy "rspamc-learn-ham.sh";

The actual learn trigger is a simple one-liner /var/vmail/conf.d/rspamd/rspamc-learn-ham.sh:

exec /usr/bin/rspamc learn_ham

Classifying Spam is straight-forward based on the triggers defined in Dovecot. If a message is copied to the Spam mailbox it will be learned as Spam.

/var/vmail/conf.d/rspamd/report-spam.sieve

require ["vnd.dovecot.pipe", "copy"];

pipe :copy "rspamc-learn-spam.sh";

/var/vmail/conf.d/rspamd/rspamc-learn-spam.sh

exec /usr/bin/rspamc learn_spam