How exactly are you trying to import the address book? Is it from a file exported from another Thunderbird installation or other program, or are you trying to import it directly from another Thunderbird installation, or is it an on-line address book such as Google Contacts?

If option #1, the answer would be, 'whatever format you had chosen to export it to.' If you have a choice, I recommend VCF (vCard) format.

Hi Lin. Well, it didn't work, so I think I need to give you more information. I have an online email account with my internet provider. I have installed Thunderbird on my Android phone and use it with an Imap connection. However, I don't have the Thunderbird app installed on my laptop. I hope this helps, and thank you very much for your reply to my problem!