Other mail servers

Spam Scanner speaks four protocols, so most mail software can use it without a plugin of its own:

Protocol	Command	Used by
Milter	`spamscanner milter`	Postfix, Sendmail, OpenSMTPD (with filter-milter)
spamd	`spamscanner spamd`	spamc, Exim, Haraka, and anything written for SpamAssassin
HTTP	`spamscanner http`	Scripts, webhooks, custom MTAs and services
Pipe	`spamscanner scan`, `spamscanner filter`	Postfix pipes, procmail, maildrop, cron jobs

Postfix and Sendmail have their own page.

A drop-in for SpamAssassin's spamd#

spamscanner spamd answers SpamAssassin's spamd protocol: CHECK, SYMBOLS, REPORT, REPORT_IFSPAM, PROCESS, HEADERS, PING and, with --allow-tell, TELL. Software written for SpamAssassin works unchanged; stop spamd and start Spam Scanner on the same port.

Shell

sudo systemctl disable --now spamd    # or spamassassin, depending on the distribution
spamscanner spamd --port 783 --auth

With spamc:

Shell

spamc -c < message.eml          # prints "16.3/5.0", exits 1 for spam
spamc -R < message.eml          # the report
spamc < message.eml > out.eml   # the message with X-Spam-* headers
spamc -L spam < message.eml     # learn (needs --allow-tell)

The repository's end-to-end tests run SpamAssassin's own spamc against it.

Exim#

Exim's spam ACL condition talks to spamd. In the main configuration:

Text

spamd_address = 127.0.0.1 783

In the DATA ACL (acl_check_data in Debian's exim4):

Text

  warn    spam       = nobody:true
          add_header = X-Spam-Score: $spam_score
          add_header = X-Spam-Report: $spam_report

  # Refuse mail at the reject threshold: 15 points is 150 in $spam_score_int.
  defer   spam       = nobody:true
          condition  = ${if >={$spam_score_int}{150}}
          message    = Message rejected as spam ($spam_score points)

defer answers with a temporary 4xx error, so senders retry and a mistake can be corrected. Change it to deny for a permanent refusal once results look right.

Haraka#

Haraka's spamassassin plugin talks to spamd. Enable it in config/plugins and set, in config/spamassassin.ini:

INI

spamd_socket=127.0.0.1:783
munge_subject_threshold=5
subject_prefix=[SPAM]
reject_threshold=15
old_headers_action=drop

Dovecot: Junk folder and learning#

A Sieve rule files tagged mail in Junk:

Text

require ["fileinto"];
if header :is "X-Spam-Flag" "YES" {
  fileinto "Junk";
  stop;
}

With IMAPSieve, moving a message into or out of Junk can teach the model. Start the HTTP API with a token and a model file:

Shell

spamscanner http --port 7832 --token "$SPAMSCANNER_TOKEN" --out /var/lib/spamscanner/model.json

and point the milter or spamd server at the same model with --model /var/lib/spamscanner/model.json (or SPAMSCANNER_MODEL). Restart it now and then to pick up what was learned. A script run by sieve_pipe posts the message:

Shell

#!/bin/sh
# /usr/local/lib/dovecot/report-spam.sh (report-ham.sh is the same with /learn/ham)
exec curl -fsS -X POST -H "Authorization: Bearer $SPAMSCANNER_TOKEN" \
  --data-binary @- http://127.0.0.1:7832/learn/spam

Dovecot's spam reporting guide shows the rest of the setup, which is the same for any spam filter that learns from a script.

procmail and maildrop#

Text

# ~/.procmailrc
:0fw
| spamscanner scan - --headers

:0:
* ^X-Spam-Flag: YES
Junk/

maildrop:

Text

xfilter "spamscanner scan - --headers"
if (/^X-Spam-Flag: YES/)
{
  to "$HOME/Maildir/.Junk/"
}

scan --headers exits 1 for spam. procmail and maildrop use the output, not the exit code, with the rules above.

HTTP API#

Any program that can make an HTTP request can scan mail:

Shell

spamscanner http --port 7832 --token "$SPAMSCANNER_TOKEN"

curl -s -X POST -H "Authorization: Bearer $SPAMSCANNER_TOKEN" \
  --data-binary @message.eml "http://127.0.0.1:7832/scan?ip=203.0.113.5&from=alice@example.com&to=bob@example.org"

The HTTP API lists every endpoint.

Inside a Node.js mail server#

With smtp-server, Haraka plugins or any other Node.js server, call the library directly:

JavaScript

import SpamScanner from 'spamscanner';

const scanner = new SpamScanner({authentication: true});

// smtp-server's onData handler
async function onData(stream, session, callback) {
  const result = await scanner.scan(stream, {
    session: {
      remoteAddress: session.remoteAddress,
      resolvedClientHostname: session.clientHostname,
      helo: session.hostNameAppearsAs,
      envelope: session.envelope,
    },
  });

  if (result.action === 'reject') {
    const error = new Error('Message rejected as spam');
    error.responseCode = 451;
    return callback(error);
  }

  // Deliver, with result.isSpam deciding the folder.
  callback();
}

session.envelope from smtp-server already has the mailFrom and rcptTo shape that Spam Scanner reads.