Reverse DNS Problem - 2 part Q

Okay, heres whats going on.. I have implemented RDNS on IIS5 SMTP, however, it simply changes the header information when the reverse lookup fails (RDNS failed) and allows the message through.

I would like it to reject any email comming in from a domain that cannot be verified.

A few months ago when I enabled RDNS it was rejecting emails left and right, finaly I just disabled it and went back
to strickly using blacklists after we had some problems receiving from valid sources. Now it seems that its behaviour has changed... Any ideas ?

And: Is there a way to change the error message that the rejected client receives instead of the standard "Error 550 Client host rejected" ?

Thanks in advance!

I've always extremely disliked the RDNS technique. It's like using chemo to get rid of a cancer. It kills the bad cells sure, but it also kills the good ones. At least you can control a black list.

But anyway, your question belongs in the mail server forum.

I appreciate your opinion, however, in the last 3 months weve received over 38 thousand spam messages and with all the worms going around I dont seem to have much of a choice unless you know of a better way.

I'm using spamhaus and spamcop, while they are blocking a good portion, they arent being as effective as I'd like them to be. I spent a full week with keyword filters, maintaining a black list of hosts and they still just hammer away at us.


I'll post something in the appropriate forum,

Cheers,