ETRN ACCESS mapping table

When the MTA&#x27;s SMTP server is configured to support (at least some uses of) the ETRN command (,  , or   is set, or the default behavior when no   option is set), then  the   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  mapping table have the form: transport-info&#x7c;app-info&#x7c;channel-to-run&#x7c;full-name&#x7c;claimed-system (Here   is the ETRN parameter, and   is a processed version of that parameter. See discussion of the   mapping table, or the    mapping table,  for discussion of the   and   portions of the probe string.)   If the mapping table returns a ,  ,  , or  , the ETRN command is rejected with a " " error. If the mapping table returns a   or , the ETRN is attempted. If the mapping table also returns a   or    , then the MTA tries to lookup   (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).

See also:
 * allowetrn Option
 * Mapping tables
 * PORT_ACCESS mapping table
 * ALLOW_ETRNS_PER_SESSION
 * Triggering message transfer with remote SMTP systems
 * Pre-defined mapping tables