From: Tony Earnshaw (tonnibilly.demon.nl)
Date: Sat Aug 02 2003 - 12:11:49 CDT

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Bastiaan Welmers wrote:

> One of the methods I want to use is
> smtpd_client_restricions = reject_unknown_client
>
> But there still seems to be several (poor maintained) servers without
> reverse-lookup we want to hold contact to.
> Al these servers have a HELO hostname corresponding to the IP number they use.
>
> Is there a way to configure Postfix so it will
>
> - Check if the client has a hostname
> - If not, check if the HELO hostname corresponds with the client, and if,
> don't reject
> - If both not, reject

I've never had to do this myself, but:

Is the list of misconfigured client servers small enough for you to make
a list of exceptions to a general rule of REJECT?

If it is, then the smtp.cf doc says:

# The smtpd_client_restrictions parameter specifies optional
# restrictions on SMTP client host names and addresses.
#
# The default is to allow connections from any host. The following
# restrictions are available:
[...]
# check_client_access maptype:mapname
[...]
# Permit the SMTP client if the result is OK or all numerical.
[...]

So, if you do:

smtpd_client_restrictions =
   check_client_access regexp:/etc/postfix/maps/ok_clients.regexp
   reject_unknown_client
   permit_mynetworks
   etc.

in /etc/postfix/maps/ok_clients.regexp:

/^212\.238\.97\.135$/ OK
etc.

Client access rules are acted on before helo access rules (at least
that's what my logs tell me,) so ...

Best,

Tony

--
Tony Earnshaw

http://www.billy.demon.nl
Mail: tonnibilly.demon.nl

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