topic Re: sendmail config question in Operating System - HP-UX

sendmail config question

Bill Costigan — Mon, 17 Jun 2002 16:36:42 GMT

How do you configure sendmail to prevent accepting messages from someone who has configured their sendmail to claim it's in your domain.

E.g., your domain is foo.com and your mail server will relay for foo.com. The bad guys configure their host to claim it's system1.foo.com and they send you mail to relay.

Can sendmail be configured to do a reverse IP lookup to see if the sending IP address is really who they claim to be?

Re: sendmail config question

harry d brown jr — Mon, 17 Jun 2002 18:14:11 GMT

Bill

sendmail is the beast of hell to modify the configuration

try this link:
http://www2.hunter.com/~skh/spam/sendmail.adds.html

better yet, hire a sendmail expert.

:-))

live free or die
harry

Re: sendmail config question

Mike Hassell — Mon, 17 Jun 2002 21:06:18 GMT

Bill,

I don't have a real solid answer for you, but you may wish to look into FEATURE(relay_hosts_only), that is if you can define all the hosts in domain.com that you want to relay mail for. Take a look at the following link that may lead you in the right direction:

http://www.sendmail.org/tips/relaying.html

Hope that helps, but as Harry says, sendmail config can be a real pain in the ass, as I'm sure you're already aware of :-)

-Mike

Re: sendmail config question

Jordan Bean — Mon, 17 Jun 2002 21:48:12 GMT

If you have version 8.9.3 (PHNE_18546), then have a look at the Anti-spamming section of /etc/mail/sendmail.cf (around line 560) for immediate options.

Otherwise, think about upgrading to the latest version and build a new config file with the really cool anti-spam and security features.

Re: sendmail config question

benoit Bruckert — Tue, 18 Jun 2002 06:49:58 GMT

The best way is to use anti-relay feature.
add in your cf file :
FR-o /etc/mail/relay-domains
and store in this file domains (or ip addresses may be it work with subnet ???) for which relay is enable.
sendmail is doing a reverse lookup (at least with version 8.11.6) because i'm using it.

hope it 'll help

Re: sendmail config question

Bill Costigan — Tue, 18 Jun 2002 18:45:46 GMT

Thanks for all the hints.

I'll go to the various links and see if I can figure out how to close the hole.

I'm already running 8.9.3 and are using some of the anti-spamming features. But I must have left something open.