how does a 'generic' email like that get sent to a personal address?
The "To" field, listed in the mail headers, is not what the MTA uses to determine to whom to deliver the mail. The recipient is specified by the sender during the SMTP conversation between the two servers. So the sender puts one thing in the "To" field, but tells your ISP's server to deliver the mail to you, which it does. Anyone can put anything in the "To" header.
are THEY doing everything they can to stop the spread of this stuff?
Who knows? An ISP getting paid next-to-nothing is unlikely to be interested in setting up custom mail-handling for a customer.[/quote]
should I be really have to place x hundred filter rules to stop this?
If your mail client is sophisticated enough you could set up rule which says "reject anything where my exact email address is not listed in the 'to' header".
surely any 'generic' address which is NOT on the provider's list should be blocked?
Not quite sure what you mean by a generic address, but the explanation above describes what is happening. Your ISP aren't doing anything wrong - they are just delivering mail that was addressed to you.
should I keep on nagging?
I doubt they'll listen.