I've evaluated several solutions for sending email to large groups. My favorite software solution is Gammadyne.
The interface is downright ugly, but it has such powerful scripting capabilities, a built in language called G-Merge for data manipulation and the ability to plug into almost any database, that I can't help but love it. I thought I'd bring it up, since the holidays are coming and those of you who are slow to get out your paper christmas cards (you know who you are!) could sign up for a Gammadyne trial and send out 'emailed' christmas cards instead. Just a thought.
Download a trial version of Gammadyne or purchase it now.