I have purchased the ShiftThis newsletter plugin for a client, and have spent a year trying to get it to work. The program always performs well with test addresses, but has never ONCE failed to get stuck in the middle of sending to my actual mailing list. I have written to the developer, requesting support, at least half a dozen times. I have gotten only one response to the tune of "um, it should be working", and no answer at all since I have started sending him logs and screenshots. This is extremely unprofessional behavior. I strongly recommend that you do NOT spend money on any of his products - they do not work, and he will not provide support.