The description for #8 sounds more like long polling to me. For push email, I'd envision something like registering a location to send notifications to (web hooks).
Yeah, it is long polling. I could be misinformed, but isn't the problem with web hooks that you might not have ports open and could be behind a firewall?
Yea, I'd say long polling is probably a better solution in this case than web hooks since clients (likely) could be behind firewalls, NAT, and be going on and off line relatively often. Sorry, the title and description on that one just threw me off a bit - I think you chose the best option though.
