Originally Posted by PurpleGiant
Perhaps try using the 'export mail' function in OS 9, and then the 'import' function in OS X?
Can't for the life of me find anything which looks like a mail export function in Netscape 7 on OS 9...
Anyway, I solved the problem: when opening the mail window in Mozilla on OS X for the first time using the copied profile, Mozilla ignores the existing mail folders and creates new ones, so if there was an existing mail folder 'mail.example.com', Mozilla created 'mail.example-1.com' as an empty folder and ignored the original.
What I did was then: move the original mail folders to a temporary directory outside the Mozilla profile directory; start Mozilla, open a mail window, and close Mozilla. I then deleted the newly created mail folders and copied the original ones back into the profile's Mail directory. The next time I started Mozilla it was then happy to accept the "old" folders and my mail was there.