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Mailing lists module

The mailing lists module detects messages delivered via common mailing list software. It is typically used to reduce or suppress scores from rules that would otherwise trigger on list mail (e.g. bulk-like traits, footer content, or subject munging).

How it works​

The module examines standard list-related headers and known vendor-specific markers:

  • RFC 2919/2369 headers: List-Id, List-Help, List-Post, List-Subscribe, List-Unsubscribe, List-Archive, List-Owner
  • Heuristic headers: Precedence: list|bulk, X-Loop
  • Vendor markers when present, such as X-Mailman-Version, X-BeenThere, X-Google-Loop, X-Google-Group-Id, X-Listserver: CommuniGate Pro LIST

If evidence is strong (e.g. Mailman, ezmlm, Google Groups, CommuniGate Pro), the symbol is inserted with weight 1.0 and a specific result option. Otherwise, when enough generic list headers are present (score ≥ 1 from the heuristic scan), the symbol is inserted with weight 0.5 × heuristic_score (heuristic score is capped at 2, so the maximum inserted weight for a generic match is 1.0) and the generic option.

Configuration​

The module is disabled by default. It only registers its symbol and callback when symbol is explicitly set in configuration. To enable it, add a symbol entry in local.d/maillist.conf:

# /etc/rspamd/local.d/maillist.conf
maillist {
  symbol = "MAILLIST";
}

Assign a weight to the symbol in your metrics as desired (commonly negative):

# /etc/rspamd/local.d/metrics.conf
symbol "MAILLIST" {
  weight = -2.0;
  description = "Message sent via a mailing list";
}

Symbols and result options​

  • MAILLIST: inserted when a message is detected as list mail
    • Result options and inserted weights:
      • ezmlm — weight 1.0
      • mailman — weight 1.0
      • googlegroups — weight 1.0
      • cgp (CommuniGate Pro) — weight 1.0
      • generic (sufficient list headers without a specific vendor) — weight 0.5 × heuristic_score (maximum 1.0)

Supported detectors​

  • Ezmlm
  • Mailman (v2 and v3)
  • Google Groups
  • CommuniGate Pro
  • Generic RFC 2919/2369 list headers

Notes​

  • Some Mailman installations (especially Mailman 3) can disable certain List-* headers, which may reduce detection reliability.
  • The module is intended to adjust scoring for list messages rather than to accept or reject mail on its own.