[throwaway290]

1) Mentioning Google and Google account many times

2) something innocent (using Tor, using blocklisted VPN, being associated with a banned google account)

3) something you're not telling us (violating some google policy, billing address in sanctioned country, using stolen cc, I know you didn't but you asked to guess!)

[konschubert]

My guess is that it is probably 1). Somebody in their anti-spam team read "Google Calendar", saw my display and thought "Nah, that's no google calendar" :D

But maybe it was something else. It's of course possible I violated some kind of policy. But they're not sending me any debug messages :D