Spam really grates my cheese
Spam is never going to stop, because the "whole industry" never gets on board, SPF had potential, and my home mail server is setup with it, it doesn't stop it being banned because it's on a public IP, the SPF record is updated within 1-5 minutes of my IP changing.
No harm in thinking solutions though, and we have, from other posters:
- Limit to X emails a day
- Restrict the number of sign ups per day per IP
- Spamfilter the outgoing mails
I'm assuming these sweatshops just create the account, and then automated software is used to send the spam. The simple fact they're using sweatshops shows CAPTHAS are working, so stick one on the "send mail" page, requiring the sweatshops to send each mail individually, dramatically increasing the running cost for spammers, while only adding a couple of seconds onto sending mail for legitimate users.
Say 1 person can send an email every 15 seconds, copy & paste the address, copy & paste the content, add attachments, fill in the CAPTCHA. Over an 8 hour shift, that one person could send 1,920 e-mails, that's a hell of a lot less than automated bots sending God knows how many thousands an hour.
The way the UK government is going, e-mail will be banned soon anyway.