Question: So, how exactly do you prevent crime?
Answer: You kill all the victims.
This is apparently the strategy adopted by current mail server spam filters and their blind followers; mail server administrators. They are targeting email users.
Spammers are notorious for their ability to circumvent anything that spam filters have been throwing at them over the years. Spam filters have evolved from simple from header parsers into software around the 4 figure mark. And it has to be said, that despite them costing that much, spammers still happily bounce around them.
There was a time when the user was the one doing the spam filtering. This was a task that we, email end users, chose or not to do. Some of us considered spam just an annoyance, others actively sought to fight it. Regardless, the choice was on our hands. ISPs however hated spam. Most users don't understand the whats/hows/whys of spam. They complained to their ISP their box is filled with junk about penis enlargement or credit card approvals and they don't understand why they received an email from the former Minister of Finance of Chad. And so, because ISPs never really made an effort to tutor their customer base, email server spam filters became quite a catch.
Naturally spammers laugh at them. This is so because of the very nature of the email protocol. One can't simply expect to stop spam with the current rules. But spam filters claim to do just that. They claim to stop (lie) or reduce (lie) spam. What they are doing instead is killing ISP based email by implementing the only thing that is left to them to implement; draconian spam rules that ban addresses or IPs based on their overly subjective email parsing rules.
And this is exactly what I'm currently experiencing with my ISP at clix.pt. I yesterday stopped 700,000 clix.pt customers from sending emails to @xxxx.ca (let's leave the canadian ISP anonymous for now) by provoking an IP ban on the assumption my email was spam. Naturally it wasn't. It was text commands to a PBEM (Play By Email) wargame mailbot to process my turn orders. Unfortunately I typoed the address and it went to another account of the same ISP.
Because the server spam filter parser considered that spam, it didn't stop that email on its tracks, it didn't ban my email account. Nope. That wouldn't do. They know that doesn't stop spam. It instead banned my ISP outgoing email server IP address! Clap! Clap! Hurray!
As of this rant, my ISP is still banned and I'm waiting on replies from both my ISP and xxx.ca administrators.
I remember once reading something like "Spam is an annoyance. Spam filters make me lose money." You see, it's becoming more a choice of web based email, domain name email or... phone.