Although it isn't an extension - How many people are familiar with MozBackup.? Edit: I am only aware of a Windows version.
I had some minor, but annoying, problems importing mail, address books, bookmarks from IE and Outlook into my first Netscape Navigator suite many years ago. But I have never had any problems since.
MozeBackup transfers more things than you could ever want! Would you believe that MozBackup transfers your browsing history, and your cookies! If you want it to that, it does. And your passwords. It includes all your email settings, and your filters, and your folders. I download a lot of mailing lists. I have a lot of filters and folders.
Support was ended August 2004 so that Firefox and Thunderbird were relatively unknown, but it always worked fine for me. I could archive / transfer everything from Mozzilla suite. Then I imported mail and address books into ThunderBirdy and and the other stuff into Foxy. It never got hung up. It never asked any questions. If I tried to import email and bookmarks into ThunderBird, it simply reported that email was successfully transfered, but it had failed to transfer the bookmarks. No sassy talk and no insults.
No it will not combine two different emails. Importing emails overwrites all other emails. The same with bookmarks etc.
I did a little search before posting this message and learned something that I did not know. It's been updated!
![ohmy.gif](http://www.unmannedspaceflight.com/style_emoticons/default/ohmy.gif)
It now transfers extensions and themes! I haven't had time yet to check that out.
It is great for archiving your mail daily. It will archive to you choice of directories with a dated archival file. I think the new version will do it automatically.
http://mozbackup.jasnapaka.com/Jack