Should be done how YouTube does it, with a seperate inbox and notification box.
Inbox (Something you may receive in its own Email.):
[ul]
[li]Direct messages[/li]
[li]Updates from ROBLOX[/li]
[li]Billing and other features[/li]
[/ul]
Notifications (Something you’d receive in a collective Email.):
[ul]
[li]Friend Requests[/li]
[li]Comments[/li]
[li]Favorites[/li]
[li]Daily Updates on Favorited items[/li]
[li]Trades[/li]
[li]Transactions (Possibly once a day for all items, like a receipt.)[/li]
[/ul]