Hi
I am a Bluehost customer and Hostmonster and fastdomain belong to the same owner and they all have the same email policy: a limitation of 50 emails per hour. If you speak to support they may--upon hearing why you want your limit increased agree to increase it to an ABSOLUTE MAXIMUM of 500 emails per hour. The limit is not per email account but per domain.
So, if you setup 500 email accounts, they--as a group--will be allowed a total of 50 or 500 emails per hour. This is done in an attempt to prevent spam. Don't forget you are talking shared hosting here which means that there could be several hundreds of domains sharing the same server (SAME IP ADDRESS). I
f too many spam emails are identified by a given domain as coming from your server (one given IP address), that domain might block your IP address and identify it as a spam source. Given that several hundreds of domains would see their email blocked because of you, that would make a lot of angry people. Hence that policy.
So, I think you might be better off to look elsewhere.
Hope this helps