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!

I'm confused. I'm hearing so far is that you do have Thunderbird Mobile installed on your phone. But you talk about "Thunderbird emails loaded into Linux Mint on my laptop", but you also say, "I don't have the Thunderbird app installed on my laptop", which seem to contradict each other. Do you have an email program on your laptop or not, and if so what is it?

An core question is, where are your addresses now, and where else would you like them to be?