You will meet with varying degrees of success depending on the packages. There is a project called Fink that has ported a lot of packages over and provides a framework for porting others.
It would help to know the error. Several things can be checked in the ServerAmin however, there is a host configuration option that lets you list the domains hosted localy. Under each User in the User and Goups setup there is a selection for controling the user's mail. So, check if it is a...