TCP/IP-channel-specific options: ALLOW_ETRNS_PER_SESSION (integer)
This SMTP server option sets a limit on the number of ETRN commands accepted per session. The default is 1. When the limit is exceeded, the SMTP server will issue an error response to any additional ETRN command of (prior to MS 7.0.5):
550 5.7.1 ETRN session limit reached.
or as of MS 7.0.5:
458 4.7.1 ETRN session limit reached
See also the
*etrn channel options for a discussion of channel options affecting the MTA's response to ETRN commands.