Forum configuration is under Admin->Settings->Email->Email Subscriptions
Per user configuration is not available. You can open up an issue in github if you think this is something that should be added.
I have 10 invitations. If you need it, you can write your mail.
I'm a bit scared of it. Having something like this sort my mail is a bit disconcerting, and I'd prefer to do it myself or have a human do it.
But I'm old fashioned
Female PAs is quite old fashioned.
If only it worked with my Google Apps Domain. Curse me and my love for my own email address!
I tried it out for a little while, the inabilty to mark something unread drove me nuts (the snooze idea is overcomplicated IMO)