The twitter won't be an issue assuming it doesn't need anything special like special ports. The emails it generates can get you suspended rather easily though. You can send at most 50 per day for your entire account. Password reset emails should be fine, but account activation mails (even if you don't expect a lot of users, since these are generated for spambots too), new post/followed topic notifications, etc. could easily generate a lot mail. I'd disable these functions or use an external mail server for them.