If you're on a shared server, you're out of luck if you need to exceed 5-600 emails per hour (not 800). Can you "throttle" your email sending so that you don't exceed the cap (500/hr + 20/min)? PHPlist is a mailing list that can do that, to handle newsletters and such common content, but for other emails, I don't know.

Maybe someone could come up with a background script (cron job?) that accepts a stream of emails/newsletters and all the addresses to send to (ranging from "everyone" to individual users), and doles out the emails at a steady rate of 500/hr (say, 8 every minute) until the input queue is empty (individual emails could take priority over newsletters, by having multiple queues of different priority). Of course, if your average load over the course of the day exceeds 500/hr, you can't do it on a shared server and will have to look at VPS or dedicated. Another tack might be to buy 1 or 2 additional accounts and use them to offload some of the mailing load from your primary account, but at some point a VPS or dedicated would be cheaper and easier. Another problem is that you need a way for your forum, etc. to export the email address list for each request -- that would probably require some code modification (instead of sending an email directly, write a file and a list of recipients). It can be done -- it's not quite rocket science. Anyone care to try?

You're planning the next MySpace, huh?

Well, if your average load is likely to exceed 500/hr, and/or you can't afford the delay in sending emails (in order to smooth out load to within 500/hr), I don't think a shared server account is going to cut it. I can't quote any exact figures, but I understand that VPS and dedicated servers have substantially more capacity (at a much higher price, unfortunately). You'll have to email support or sales to see which you would need. You might also ask if it's possible to purchase multiple accounts (on different shared servers) to spread the load around. Other than that, you should definitely look into an external service (I presume there are some) that could handle your newsletter and other bulk mailings. LP is (or was) using such an external service for their newsletter, so maybe Mitch could suggest a name. As for non-bulk mailings, once the newsletters and such are removed, can you stay under 500/hr?

Might try this question in the presales forum http://www.lunarforums.com/lunarpages_web_hosting_plans_presales_questions-b48.0/