I'm running OZ 3.3.5 on my 5500.
The best mail client I've found so far (that I've been able to run syccessfully) is QTMail.
One drawback is that it doesn't allow me to click on embedded links (they are blue but now clickable), and it doesn't diaply attached / embedded images.

I haven't been able to get any of the variations of OPIEMAIL to run yet.. just get the error that it can't find application OPIEMAIL.

Is there a mail client around that has some of the features of a desktop client beyond the mere abiity to send and receive?