On Tue, Sep 09, 2003 at 05:12:24PM +0100, Peter Sergeant wrote: > o I'm not ready to start straight blocking email from IPs in a RBL > o Spammers operate on the margins - if I can push up their costs just > a little by tying up their mail-sending application, great > o The server doesn't recieve a huge volume of email... > o Except from mail15, mentioned previously > > Any thoughts welcomed...
To protect against dictionary attacks, do any of the standard MTAs let you configure them to slow down (or drop the SMTP connection) after sending a 550 message for a user not known? I keep thinking that forcing the buggers to reconnect whenever they are attempting such a thing is quite likely to tie them up, whilst not harming regular mail traffic. (given that I'd infer a dictionary attack is going to be at least 95% user not known 550s, and regular mail is going to be at least 95% user known) Nicholas Clark
