Is there an appropriate government office to send this information to?
Yes, there are 'datatilsynet' (Agency that is concerned with privacy issues) which I called today, the employee I talked with said I could file a complaint, dunno why he couldn't take one over the phone. He didn't seem too interested though. Don't know what I could achive by filing a complaint, not even sure if the bank would get a fine ?
And there's of course 'finanstilsynet', (Agency that's concerned that banks are adhering to the current legal framework) not so sure they would care about some e-mails sent to the wrong people.
There must be some way to anonymize your email address, spammers seem to do it all the time.
Yes, there are several free e-mail providers that I could do it through. Not sure if any of these would accept that many (hundreds) recipients though.