SYNOPSIS

       qmail-postgrey ip%netid;port Mail From: Rcpt To: TCPREMOTEIP
       TCPREMOTEHOST

DESCRIPTION

       qmail-postgrey is usually invoked by qmail-smtpd automatically
       provissioning the SMTP connection information Mail From:, Rcpt To:,
       TCPREMOTEIP and TCPREMOTEHOST to a greylising server given by
       IPv4|IPv6%netid;port.  port defaults to 60000 and thus can be omitted.
       IPv6 LLU addresses can be specified adding the netid name following the
       percentage sign.

GREYLISTING SERVER

       Since there is neiher a formal API defined for the greylisting lookup
       nor for the behavior and return codes of the greylisting server,
       qmail-postgrey only works well with David Schweikert's postgrey
       implementation.

       Here, the server's response upon recognizing the triple CLIENT_IP,
       (SMTP envelope) SENDER and (SMTP envelope) RECIPIENT is either
       action=DUNNO, action=PREPEND or action=DEFER_IF_PERMIT and in case of
       the last, qmail-postgrey returns with 10 telling qmail-smtpd to respond
       to the client with a SMTP 450 greylisted reply code. Otherwise
       qmail-postgrey returns 0.

INVOCATION

       Unlike for testing reasons, qmail-postgrey is called directly from
       qmail-smtpd in case the environment variable POSTGREY is defined and
       provissioned with the greylisting server's IP address (and perhaps
       netid and port) listening there.

       The environment variable POSTGREY is typically defined within
       sslserver's cdb.  Additionally, REPLY_GREYLISTED can be used as
       environment variable to provide some more descriptive information to
       the sending MTA which will eventually be visible in a bounce message.

CREDITS

       qmail-postgrey and its integration into qmail-smtpd is based on
       Jan Mojzis implementation and used by permission.

SEE ALSO

       qmail-control(5), qmail-smtpd(8), https://postgrey.schweikert.ch



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