[quote]1. I will manually subscribe all users to the mailing list.
4. No list commands (subscribe/digest/unsubscribe) desired[/quote]
You might want to take a close look at the DH Anti-Spam policies…these two items done this way will very easily expose you to possible (likely) Terms of Service issues.
There are many other mailing solutions out there, but you need to be familiar with DH “mass-mailing” policies before you can intelligently select a system that will work for you and keep you from running afoul of the DH TOS.