Rewrite transport substitutions

Rewrite transport substitutions, $Y, $nY
  substitutes in the  th field of the transport  information, with a plain   being synonymous with. Transport information is as it would appear in  mapping table probes, or optionally various other access mapping tables as enabled via the    MTA option,  or be logged in MTA transaction log entries, as controlled by the   MTA option (bit 1/value 2 causes generation of connection transaction entries, which normally include tranport information,  and bit 3/value 8 caused inclusion of tranport information in message transaction log entries);  that is, transport information has the format: TCP&#x7c;server-address&#x7c;server-port&#x7c;client-address&#x7c;client-port Hence for incoming SMTP/SMTP SUBMIT messages,  substitutes in  the literal string " ";   (or   which is synonymous) substitutions in the SMTP/SMTP SUBMIT server IP address;   substitutes in the SMTP/SMTP SUBMIT server port;    substitutes in the SMTP/SMTP SUBMIT client IP address; and   substitutes in the SMTP/SMTP SUBMIT client port.

If  and      is used in a rewrite rule template  but transport information is not available for the address being rewritten, the rewrite rule will fail.

See also:
 * PORT_ACCESS mapping table
 * include_connectioninfo MTA Option
 * log_connection MTA Option
 * Rewrite rule template substitutions and control sequences