I have a really simple algorithm to reporting something as spam:

> Was this email solicited by me?

The author describes unsolicited emails and somehow misses the point that spam is a term for unsolicited emails.

The reminder email in your list sounds unsolicited, so I'd probably report that one as spam as well. I wasn't aware it was mandatory, probably because it's not where I live.

My transactional inboxes are mostly clean as a result. My "spam" inbox, however, is full of crap (the email I use to sign up to freemium services).