ETRN_ACCESS mapping table
When the MTA's SMTP server is configured to support (at least some uses of) the ETRN command (
silentetrn is set, or the default behavior when no
*etrn option is set), then the
ETRN_ACCESS mapping table can be used to exert more precise control over which SMTP clients are allowed to issue which ETRN commands (and optionally control over what channel is actually run as a result of the ETRN command). Probes of the
ETRN_ACCESS mapping table have the form:
claimed-system is the ETRN parameter, and
full-name is a processed version of that parameter. See discussion of the
PORT_ACCESS mapping table, or the
MAIL_ACCESS mapping table, for discussion of the
app-info portions of the probe string.) If the mapping table returns a
$f, the ETRN command is rejected with a "
459 4.5.0" error. If the mapping table returns a
$s, the ETRN is attempted. If the mapping table also returns a
channel-name, then the MTA tries to lookup
channel-name (in the channel/host table from the configuration file) and if that lookup is successful, runs that channel (rather than whatever channel the original ETRN command might have run).