455
deinitely not XOOPS then as herko says, XOOPS doesn't use perl at all..
it may use smtp if you have set it up to use smtp otherwise it uses phpmail, or if you have a mailing list manager with a lot of subscribers?? in which case if you are using mailing lists and you have more than a couple of thousand subscribers then yes, ideally you do not want to be on shared hosting plans.
what does your host class as a lot of emails?
hell 1 of my sites sends around 70,000 emails a week (due to mailing lists mainly)