Email list server installation with minor modification.

We need to have a program installed or developed to allow us to send emails to a list of up to 100,000. We need a place to host this (our current server is not an option) so we would like the selected provider to either offer this service or point us to a quality service for this. The email list server does not need to be complex at all, we just need the very basic features, such as: subscriber management w/auto unsubscribe and bounce features, open/click through tracking, setting up campaigns (html and text), etc .. see [login to view URL] or any similar email list host (we just need their more basic features). We will need 1 modification however (i'm not sure how this works or if perhaps there're programs available with this feature already but i'm open to ideas on how this can be done, etc but here's the general break down). In the email storage management in terms of emails previously sent we need the function to display x# of past emails and we need to be able to change this number. What i mean is i have to be able to for example set this number to 5 or all from the last 7 days and in that case only those emails should appear and all others that don't fit the criteria must be gone from the database.