Re: A security issue of a different kind.

[alan () manawatu gen nz (Alan Brown)]

This from the 8.8.3 release notes:

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8.8.0/8.8.0     96/09/26
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        After 25 EXPN or VRFY commands, start pausing for a second before
                processing each one.  This avoids a certain form of denial
                of service attack.  Potential attack pointed out by Bryan
                Costales.
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        Define new macros ${client_name}, ${client_addr}, and ${client_port}
                that have the name, IP address, and port number (respectively)
                of the SMTP client (that is, the entity at the other end of
                the connection.  These can be used in (e.g.) check_rcpt to
                verify that someone isn't trying to relay mail through your
                host inappropriately.  Be sure to use the deferred evaluation
                form, for example $&{client_name}, to avoid having these bound
                when sendmail reads the configuration file.
        Add new config file rule check_relay to check the incoming connection
                information.  Like check_compat, it is passed the host name
                and host address separated by $| and can reject connections
                on that basis.
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