Migrate from Evolution to Thunderbird

Very easy:

1. locate your evolution mail folder.
   e.g. ~/.evolution/mail/local/
   
2. locate your thunderbird mail folder.
   e.g. ~/.thunderbird/sdfesfbox.default/Mail/pop.gmail.com/
3. copy Inbox, Outbox, Sent, Drafts files in your evolution mail foder,
   to your thunderbird mail foder.
   (It will overwrite the the files in your thunderbird mail folder, click
   "yes" if you want them to be replaced)
4. Very easy right? Just copy every files from your evolution mail folder, WITHOUT any extension.(Berkely mailbox file type, if you re curious) That means if you have created a sub-folder in evolution, find the sub-folder, and copy the file to the thunderbird mail folder.  
5. Restart thunderbird, the new Inbox, Outbox, Send, Drafts, (and any other mail files you copy over), will show up. You can arrange them, create folder, and organize them if you like.