Asked Questions on NetAuth
Yes, and using any mail server you want to but with limited features and functionality. To do this your mail server must be set-up to use an external authentication module to verify users.
The most important changes from version 2 to version 3 is that the ini file settings have changed and new ones were added, the instructions for converting an existing version 2 ini to a version 3 ini are in the main NetAuth documentation http://www.netwinsite.com/netauth/netauth.htm. The install program nasetup should hanlde the copying of new images, templates and documentation. Old NetAuth images will not be removed so you will have to do this by hand if you no longer want them.
After an upgrade if users created with the new version of NetAuth are no longer being recognised by you mail program then the reason is that you have not correctly set up the ini setting 'suffix'. NetAuth version 2 did not allow flexibility in user creation and assumed a suffix value, NetAuth 3 allows you to set this value.