[H-GEN] Sendmail and open relay

[Robert Brockway]

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On Mon, 28 Jul 2003, Tony Melia (DMS) wrote:

> I am running sendmail 8.12 in a redhat 7 box which is working great.  I
> configured it to reject mail using normal anti-spam rules.  However, I do
> have a need for some remote to send me mails to alert me on backups -
> however because these remote servers do not use DNS, sendmail rejects their
> mail since it fails reverse lookups.  Is it possible to configure a top
> level rule which says allow mail to be received from these hosts if the from

It's even easier than this.  As long as /etc/nsswitch.conf is configured
properly[1] then simply add an entry
to /etc/hosts.  Sendmail should then see this and accept the existance of
a reverse lookup.

> address is allowmail at mydomain.com or something like that?? i.e allow mail

You could look at using SASL to allow relaying only to authenticated
hosts.  Easdy to setup under sendmail (many Linux distributions already
have it eady to go).  Not sure about SASL support in Exchange.

[1] The file /etc/nsswitch.conf should contain something like this:

hosts:          files dns

Be careful changing /etc/nsswitch.conf unless you know what you are
doing.  You really can break the system badly and require emergency
boot media to get back in[2].

[2] Actually a workmate locked himself out of his system doing this
recently.  I was able to get in using the "init=/bin/sh" trick detailed in
http://robert.timetraveller.org/tips (tip #2).

Rob

-- 
Robert Brockway B.Sc. email: robert at timetraveller.org  ICQ: 104781119
Linux counter project ID #16440 (http://counter.li.org)
"The earth is but one country and mankind its citizens" -Baha'u'llah

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