I've been researching mail filtering software on and off for a while, but have realized one big drawback to those I've seen so far: They don't do validation of recipient e-mail addresses. Since they're separate from the actual messaging server, they don't have the ability to know if user1@mydomain.com is a real account or not. It simply receives the e-mail, scans it, then passes it on to the messaging server if it passes the tests. Of course, then the messaging server would have to bounce it back to the "from" address.
The overall problem is that it wastes lots of bandwidth and processing power. If a spammer sends something to an invalid account, the filtering program has to scan it and pass it onto the messaging server, which then has to try and return the message. If the return address is bogus, then the postmaster has to get involved, wasting real human time.
(This can be compared very well to the problem that Netscape Messaging Server 3.6 doesn't reject illegal relays at the protocol level. The server accepts the message, then tries rejecting it. Wasted processes, wasted bandwidth. NMS 4.15, by contrast, will reject it at the protocol level, and the only real effort that's been expended is the SMTP connection.)
Does anyone know of a good filtering/scanning application that can be aware of e-mail accounts without having to program them in separately? Maybe one that can query the LDAP server to see if an address is valid?
Thanks!
The overall problem is that it wastes lots of bandwidth and processing power. If a spammer sends something to an invalid account, the filtering program has to scan it and pass it onto the messaging server, which then has to try and return the message. If the return address is bogus, then the postmaster has to get involved, wasting real human time.
(This can be compared very well to the problem that Netscape Messaging Server 3.6 doesn't reject illegal relays at the protocol level. The server accepts the message, then tries rejecting it. Wasted processes, wasted bandwidth. NMS 4.15, by contrast, will reject it at the protocol level, and the only real effort that's been expended is the SMTP connection.)
Does anyone know of a good filtering/scanning application that can be aware of e-mail accounts without having to program them in separately? Maybe one that can query the LDAP server to see if an address is valid?
Thanks!