syntax: xclient on | off
default: on
context: mail, server
With this directive you can enable or disable the command XCLIENT with the connection to SMTP backend. This allows the backend to enforce limitations on the client based on IP/HELO/LOGIN.
If xclient is enabled then nginx first transfers to the backend:
EHLO server_name
Then:
XCLIENT PROTO=ESMTP HELO=client_helo ADDR=client_ip LOGIN=authentificated_user NAME=[UNAVAILABLE]