[Zope] exUserFolder mysql authentication, password question

Hi, I'm currently looking into the possibility of replacing our own home-made content management system with Zope/Plone. We have a mysql database we will want to continue to use. I have installed exUserFolder, to be able to use user information stored in this database for authentication. Now that's almost working, the only thing is that exUserFolder is expecting passwords to be encrypted; which they are not. Is there a way of telling exUserFolder that it should work with non-encrypted passwords? Thanks, Ivar van Duuren