For some reason thunderbird still does not support an automatic way to import these .mbs files generated by Opera although it uses the format it self.
The procedure is quite simple and all you have to do is the following: First you have to find the folder where the mails are saved by thunderbird on your hard drive. That is on:
Tools->Account Settings->Local Folders->Local directory
By default this is:
where <user_name> is the username of the user (as in windows username) and the <random_sequence> is a random sequence of characters.
There you will find files with no extension accompanied by files with the .msf extension. If you have created any subfolder you will see folders with the foldername.sdb format.
- To import your email create a folder in the Local directory (e.g. importedmail.sdb). You have to stick with that name to the following steps (that is importedmail).
- Then inside the folder copy the .mbs file and rename it to importedmail with no extension
- Copy the mbs file again this time rename it to importedmail.msf.
- Restart thunderbird and wait for a while. A importedmail folder should appear under the Local Folders. After that you can copy these emails to a mail account.
I tried to create he folders directly in a gmail account but thunderbird wouldn’t find the mails. Thus I first imported to the Local folders and then copied to the account.