topic Re: Block Spoof mail in Operating System - Linux

Block Spoof mail

Leovino A. Trinidad, Jr — Mon, 17 May 2004 05:58:54 GMT

Hi!

How do you block spoof mails? I've read that is by using mail domain reverse lookup but how can I do that?

Regards,

LAT

Re: Block Spoof mail

Joel McClung_1 — Mon, 17 May 2004 08:44:30 GMT

I use SpamAssassin (http://www.spamassassin.org/) on my home network and I've been quite pleased. I get almost 200 spams a day, and SpamAssassin does an excellent job of marking them.

Spamassassin puts extra headers in the email message that mark it as spam or not, and your email-reading program can decide what to do with the ones that are marked as spam.

In my case, I use pine to read email, so for the first few weeks, I arranged for pine to move the messages to a "SPAM" folder so I could make sure I had everything set up properly.

Now, I just let pine delete them.

Joel

Re: Block Spoof mail

Fred Ruffet — Mon, 17 May 2004 08:57:29 GMT

Have a look at this thread :
http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=450771
It's in the HP-UX forums, but it's all about sendmail.

Regards,

Fred

Re: Block Spoof mail

Steven E. Protter — Mon, 17 May 2004 09:40:31 GMT

This thread says how to do it.

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=450771

The problem is, nobody I know besides aol has it working.

So, give it a shot and i'll try it at the same time and help you get it done.

Don't worry that its an hpux thread. sendmail is sendmail is sendmail.

SEP

Re: Block Spoof mail

Steven E. Protter — Mon, 17 May 2004 09:50:58 GMT

oops. didn't read Fred's post carefully.

:-)

SEP

Re: Block Spoof mail

Leovino A. Trinidad, Jr — Mon, 17 May 2004 21:47:57 GMT

Thanks for that helpful info. I tested it and it worked.

Another problem of mine is, how can I block a mail that comes from a valid domain but uses an invalid user address (no such account in the mail server)?

For the sake of others, to make the steps more clear about doing HACK(require_rdns) do the ff.(I found this on the net):

1) create a file named "/usr/share/sendmail-cf/hack/require_rdns.m4"
whose contents are listed at:
<>

2) put a line in the sendmail.mc

HACK(require_rdns)dnl

3) build a new sendmail.cf (based on my locations of files)

# m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf

4) restart sendmail and enjoy a whole new world of rejected mail from
spammers and mail from poorly configured dns.

5) wait to see if there are any false positives.

Re: Block Spoof mail

Steven E. Protter — Tue, 18 May 2004 01:05:57 GMT

Something wrong with the link

http://www.cs.niu.edu/~rickert/cf/hack/require_rdns.m4

Thanks for documenting the whole process.

SEP