I have been using Mozilla Mail and later Thunderbird for my email for around five years. My mail folders contain over half a gigabyte of communication, that I definitely do not want to lose. So moving to Linux, I also had to move my mail.
While Thunderbird has features to import email and settings from other mail programs, like Outlook and Pegasus, it does not have an option to import from another Thunderbird installation.
My first attempt of just copying all the mail folders from my Windows profile to the Linux profile did not work as expected. Most of my mails got copied, but some older ones seemed to get lost.
After browsing a bit, I found an explanation of how to do it properly, namely by copying the whole profile instead of just the mail folders. This way, all settings and spam filter training, etc. also get copied – very nice!
First step is to set up a new profile in Thunderbird. This will get stored under “~/.thunderbird/xxxxxxxx.default” (where xxx is some kind of hash value). Next, copy all files from the Windows profile (under Documents and Settings/Application Data/Thunderbird/xxxxxx.default) into the Linux profile. This may or may not include your mail folders, which by default are stored under the profile, but may be customized. In my case, the mail folders were on another drive accessible to both Windows and Linux, so I just let them stay there.
In the profile data is a file called prefs.js. This include the setup of email and newsfeed accounts. In this file are paths to the mail folders. In the Windows profile, these point to something like C:\…\…\. These obviously do not work under Linux, so edit all occurrences to the new path, e.g. something like /home//.thunderbird/xxxxxxx.default/… Make sure the profile and mail folders are read and writeable.
Starting up Thunderbird, you should now see all you mail and settings.