Alberto, > You run the risk of starting a DoS attach against your own box. > The RFC's state that senders should keep trying for ~5 days > > Quote " > : Chances are that you would get more DoS by new connections constantly > : coming in, than by 5xx responses causing at least protocol-compliant > : senders to give up." > Search for tcp wrappers in comp.mail.sendmail for details
The problem is that we're not dealing here with protocol-compliant senders. We're dealing with spammers who either ignore the 5xx response and keep trying, or who have a seemingly endless supply of garbage to send, all of which gets the 5xx response after I've incurred considerable processing time working out that it was spam. TCPWrappers would normally help, but it is too late in the process (they've already connected to the SMTP server), and too lacking in future possibilities such as delayed responses and tarpitting. In many cases, the spammer will happily still send their data down the pipe, even though every request gets a 5xx response immediately. You can't expect them to play nicely. Best Wishes, Paul. __________________________________________________ Paul Murphy Head of Informatics Ionix Pharmaceuticals Ltd 418 Science Park, Cambridge, CB4 0PA Tel. 01223 433741 Fax. 01223 433788 _______________________________________________________________________ DISCLAIMER: This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to which they are addressed. If you have received this email in error please contact the sender or the Ionix IT Helpdesk on +44 (0) 1223 433741 _______________________________________________________________________
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