Hi-
Why not take your messages and put them in a queue, flat file or mysql db, then have one or a few background jobs that doing nothing but loop, process mail, sleep to do all the sending.

In your queue file you would know what personalised setting to use and etc.

I do the same thing, kinda, I take interface files from the as/400, make either pdf's or excel spreadsheets, then email them to vendors and such.

I use Mail::Sender and not have to rely on sendmail.

ronzo