Options for sending emails from VPS website

I run an asp.net poetry community/forum website that emails users when their poems receive comments (If they have this feature enabled). It’s a fairly active community. However, myhosting.com puts a limit on how many emails can be sent from VPS servers they host. They only allow 100 emails per hour. I don’t know how many emails my website sends an hour, but I’m sure it more than 100. What options are there for sending emails from a VPS website? I don’t want to be constrained by this 100 email limit since it hurts my community.