A LITTLE Exchange open relay

[MichaelDOM2005]

We discovered that today, our Exchange 5.5 server had absolutely no security on it whatsoever, and it was a 100% open relay. After following posts and web pages to secure the sever, we have pretty much eliminated everything by checking the two top boxes in the relaying restrictions box of IMS.

However, the server will still allow messages to be relayed that match the domain that's on the mail server. For example, if my email domain is cheese.org and joe@swiss.com tries to send to someone @cheese.org using our SMTP server, the message will be relayed to the user. But, if joe@swiss.com tries to email anyone outside of the cheese.org domain using our SMTP server, the message is refused and he gets the 550 error.

So, how can we close this final small loop to prevent spammers from relaying to the local domain?

Thanks friends!
Michael.

 

[Dyadmin]

I'm assuming swiss.com is part of your listed domains, and if the spammer tries to send spam pretending to be part of your domain but really he is not. Then I think the best solutions is 3rd party. You can make the exchange IMC (internet mail connector) refuse email from people outside your domain, but that would be an administrative nightmare. So 3rd part is the best solution.

I use Xwall myself and I've been very happy with it. Very light on the server and runs swimmingly.