Desktop Bulk-Emailer Suggestion?
I want to send email to a list of people at a certain interval without getting them detected as spam.
You want a proper mailing list manager then. Mailman is what you're looking for on the linux side. List management will help you prevent yourself actually being spam too.
You might consider some kind of Groups application provided by a large, multi-national corporation.
If you are part of a large, multi-national corporation, and you follow the anti-spam laws, your email should get through. If you are part of a small organization, consider using Yahoo Groups, the Google equivalent, or similar group management application. Then you can be sure that your emails get through, at least to the end-user's spam filter, and that you can't shoot yourself in the legal foot by unwittingly sending unsolicited emails.