Regarding a good but not to hard RBl and upgrade/reinstall

[Anders Andersson, IT]

Hi
I was planning to use an RBL in sendmail but Im not sure
which one to use. Since IM not to experinced at this
I was hoping somone could recommend a good but pretty
safe RBL. We prolly get around 500 msg's a day that makes it
all the way to exchange and then get bounced.
Planning to make a routine for extracting adresses from
exchange and build aliases but this could be a short cut until
thats done.... any  suggestions?

Oh, btw, any recommendation regarding upgrade to newest version.
Uninstall prevous or just do upgrade?

/Anders