On Tue, Sep 26, 2006 at 12:29:08PM -0500, /dev/rob0 wrote:
Furthermore, users rarely understand how mail works. They think that sender addresses really mean something. You got spam from some sender address, so you should blacklist that address? Well duh, it probably wasn't really that sender. Maybe you just blocked a real person, an innocent victim of spammers.
Here's why we have white/blacklists at ISPs at all.
Whitelisting at ISPs is usually provided for users who receive mail from broken automated systems that trip over heuristic spam-detection filters (i.e. spamassassin and co). Telco Fax/SMS gateways are a typical culprit, and badly coded feedback forms at websites.
Blacklisting at ISPs is usually provided for people to block spew. It is a mistake to provide it alongside anti-spam controls.
Both are cheap hack solutions, but it is never worth an ISP's time coming up with a sound and correct solution (usually - fix an external, customer 3rd party source) for what is commonly an isolated case. So, these imperfect but generic tools suffice.
JG