anti-spaming

[peters1977]

I am trying to protect my mail server running sendmail 8.9.3 against spamming. From what I understand there are several ways to do this. But I need to allow Outlook express users to send email to anywhere on the internet, but only qualified users. How can this be done?

Thanks for help

 

[AndyBo]

Are you trying to prevent spam from being generated internally? Or is this two questions in one? ie, how do I stop incoming spam? + how do I only allow authorised users to send e-mail via the internet?

On the spam side of things, take a look at

http://www.sendmail.org/m4/anti-spam.html

This details various methods of blocking incoming spam, including the use of RBL lists.

I'm not sure on the user authorisation issue. The easy answer is to suggest that you uninstall Outlook Express from PCs that don't need Internet e-mail. The problem there, though, is that the users lose internal e-mail as well...

A more "difficult" solution might be to put a good Acceptable Usage Policy in place, and get people to sign it. (Once your legal advisors have given it a look over...) Then give everyone external e-mail access. If anyone breaks the AUP, they can have disciplinary action brought against them.

I don't know of any technical solutions to the authorisation issue. The problem here is that SMTP does not do user authorisation. A kludge may be to install two mail servers. One of them has an internal domain name that everyone uses for day to day mail. The second acts as a mail relay to the Internet. POP mailboxes for incoming Internet e-mail are held on the Internet server. You set up two accounts in Outlook for authorised users. One for the internal mail server (that everyone uses), and one for the Internet mail server.

If you wanted to make things a little more transparent, you might want to install fetchmail on the internal server. This could retrieve mail from the Internet server and direct incoming mail to the appropriate accounts on the internal mail server.

Only authorised users would have POP accounts on the Internet server. Anyone else will quickly realise that it's not much use being able to send mail to the Internet without being able to retrieve it... (That's assuming that you let the internal mail server relay mail to the Internet mail server.)

Sorry for rambling on! It's late on a Friday afternoon, and I've just core dumped some ideas that I've had in the past. Hope there's something useful in here for you.