I am looking for the best way to implement a procedure that runs once a day
and emails user's if their password is about to expire in 30 days. Lurking a
bit I have found

a) Identity Manager 3.5 Job function. I had seen a sample java job floating
around, can't find anymore.
b) A Coolsolutions Password Driver. However it looks like it builds a
nodeset. I have 320,000 users I have to imagine that will not handle it.

I appreciate any ideas.