Hi all,

I'm a newby in configuring sendmail and can't find some way to prevent
unresolved host names to send me emails.
If a remote host issue a connection to my sendmail and if its IP does not
resolve I don't want to receive any email from it (just close the connection
or send back a 550/420 SMTP code).

It's probably a very basic sendmail configuration but no idea to make it...


Thanks a lot.

....

On 08/23/07 07:07, Ed cor wrote:
> I'm a newby in configuring sendmail and can't find some way to
> prevent unresolved host names to send me emails. If a remote host
> issue a connection to my sendmail and if its IP does not resolve I
> don't want to receive any email from it (just close the connection or
> send back a 550/420 SMTP code).

*nod* "Require R(everse)DNS hack(s)".

> It's probably a very basic sendmail configuration but no idea to make
> it...

Well its not as simple as turning an option on in your .mc file if that
is what you are thinking. Search this news group for "Require RDNS" or
"Require Reverse DNS" hack(s) to find out how to do it.

Don't fear, what you are wanting is not un-heard of, just not all that
common.



Grant. . . .

Grant Taylor <gtaylor@riverviewtech.net> writes:

> On 08/23/07 07:07, Ed cor wrote:
>> I'm a newby in configuring sendmail and can't find some way to
>> prevent unresolved host names to send me emails. If a remote host
>> issue a connection to my sendmail and if its IP does not resolve I
>> don't want to receive any email from it (just close the connection
>> or send back a 550/420 SMTP code).
>
> *nod* "Require R(everse)DNS hack(s)".

Sendmail-8.14 supports/contains FEATURE(`require_rdns')

<quote src="RELEASE_NOTES">
8.14.0/8.14.0 2007/01/31
[...]
CONFIG: New FEATURE(`require_rdns') to reject messages from SMTP
clients whose IP address does not have proper reverse DNS.
Contributed by Neil Rickert of Northern Illinois University
and John Beck of Sun Microsystems.
</quote>

Use the non sendmail.org HACK only for pre 8.14 sendmail.


> [...]

--
[pl>en: Andrew] Andrzej Adam Filip : anfi@priv.onet.pl : anfi@xl.wp.pl
Indomitable in retreat; invincible in advance; insufferable in victory.
-- Winston Churchill, on General Montgomery

Ed cor wrote:
> Hi all,
>
> I'm a newby in configuring sendmail and can't find some way to prevent
> unresolved host names to send me emails.
> If a remote host issue a connection to my sendmail and if its IP does not
> resolve I don't want to receive any email from it (just close the connection
> or send back a 550/420 SMTP code).
>
> It's probably a very basic sendmail configuration but no idea to make it...
>

Look at my sendmail.mc -- http://www.borgnet.us/sendmail/sendmail.mc

At the end I have my own LOCAL_RULESETS and in it I have Scheck_mail and in
that rule I have exactly what you are looking for.

-- Scott