Once received module

This module is intended to do simple checks for mail with one Received header. The idea behind these checks is that legitimate mail likely has more than one received and some bad patterns, such as dynamic or broadband are common for spam from hacked users’ machines.


The configuration of this module is pretty straightforward: specify symbol for generic one received mail, specify symbol_strict for emails with bad patterns or with unresolvable hostnames and add good and bad patterns. Patterns can contain lua patterns. good_host lines are used to negate this module for certain hosts, bad_host lines are used to specify certain bad patterns. It is also possible to specify whitelist to define a list of networks for which once_received checks should be excluded.


once_received {
    good_host = "^mail";
    bad_host = "static";
    bad_host = "dynamic";
    symbol_strict = "ONCE_RECEIVED_STRICT";
    symbol = "ONCE_RECEIVED";
    whitelist = "/tmp/ip.map";

IP map can contain, as usually, IP’s (both v4 and v6), networks (in CIDR notation) and optional comments starting from # symbol.