Thanks for the replies.
First of all, we do not spam. We are running a small but legit software company that needs to send out mass email (is 700+ really a "mass"?) to our paying customers once in a while (like every few months). I'm just as afraid of being labeled as spammer as the hosting provider, because we completely rely on emailing as our essential marketing/distribution/service channel. If our domain is blacklisted, we are doomed. So that you know where we are coming from.
Is 700+ messages really that a big number? I'm sure we are at the bottom of business hierarchy. Probably 99% of business out there should have bigger mailing lists than us, no?
Also, the server provider actually allows 750 emails per hour. I only need about that many a day when we are busy. So this "20 messages a send" cap is a very strange restriction to me. I can't really understand its reasoning.
I have tested again on our server by manually composing 20+ messages and sending them out as a test. The cap is still there, so the level1 support's explanation was false (the claim that thebat's faking unique email and if I compose the messages manually it would work blahblah). It seems to me like a hard cap on all send sessions above 20 messages.
What would be the alternative to thebat then? I always thought thebat's features are adequate for the mass-mailing purpose - besides its weak handling of group organizing (address book).
BTW, the hosting provider has been pushing the idea of using a few php programs that they endorse. I'm very reluctant to the idea. I don't want an open mailing list php program. We don't want an open mailing discussion list. And we need to CONTROL and CLASSIFY each customers' status so we can easily identify and customize the messages to his group. And the data have to be changed frequently. And it has to be portable - who knows how long we will use this server provider. I'm very uncomfortable about using a script program on a faraway server for this task.
So, I'm looking for something that can be customized with templates, and has excellent group organizing features, and now preferably has extra features to defeat the 20-messages cap. What would you experienced guys would recommend?