Infinite scroll suits some people. Notably Yahoo Groups and Groups.io have both adopted that style for for presenting message lists and messages in topic.
Infinite scroll doesn't suit me at all. I want to get to the bottom of the screen - especially if I want to save it!
What I would suggest would be to have some list/message viewing options, with facile ways to switch among them, so that one can choose the style that works best for what you're doing at the moment.
If it could be turned on or off by the user, that would be nice for both camps.
