for interspire, any cpanel hosting with PHP and MySql will work fine. If you send 24 hours a day, you are theoretically under many hosting limits of 500 emails per hour. Unless you have a very clean list, you will need to throttle your send rate in interspire down to 250 an hour to account for bounces, bounce processing, replies, etc. And, an couple of spam complaints and the big hosting providers like gomamma and hostlizard will shut down your account. So I have found that you really can't do more than 8k to 10k per day and keep your domain/hosting account up for any length of time.