Ultima Hosts Worldwide Windows Hyper-V VPS Hosting

I'm building a site that sends out theft advisories to an organization's membership and law enforcement.  Data is in a SQL Server database maintained by the app.  Currently, when a notice needs to go out, a new mail message is created and addressed to recipients that were selected for that particular message (such as range from a starting zip code, all subscribers within a particular state).  The number can vary considerably based on the criteria.  It works, but I'm concerned about performance as the number of subscribers grows over time.  (Some messages could have hundreds of recipients, though most are 50 or fewer.)

I'm wondering if it's possible to dynamically create a temporary mailing list for each notice consisting of only the selected recipients from within code, then delete it once it has been sent.  Would this approach be more efficient for messages that need to go to a large number of recipients, rather than sending regular mail messages with lots of BCCs?  Or, are there other strategies for handling large mailings?

If there is an API for creating/editing a mailing list, where can I find the documentation for it?

I don't think there is a direct API with the Mailing List feature.  These are the only API's (web services) I could find:  mail.yourdomain.com/services/svcuseradmin.asmx

Why not just change your code to loop through the list of recipients and send them in groups of 50 (or whatever number you'd like).  That way you can ensure that even if a distribution has 200 recipients that only 50 are sent at a time.

I'm doing batches of 75 recipients.  The reason I brought this up was I recall a discussion about restrictions the mail system imposes in terms of the number of times a domain client can hit it in an hour (of course, I can't find it).  I also read something (don't remember if it was here or elsewhere, and I can't figure out how to get Google to give me that one again either) about SmarterMail handling sending to mailing lists more efficiently than individually-addressed mail messages.  The key here is I don't want to bog down the mail server or the app with more CPU or bandwidth than is necessary.

I did find the documentation for creating and manipulating mailing lists from code on the SmarterMail site.  I was hoping to get some input from other devs who have done it, or Mark, about whether it makes sense/is preferred that I go that route.