The release notes for Thunderbird version 60 state that FIDO U2F is supported. Unfortunately it doesn't mention any email providers that it works with. It appears that it might not just be a question of whether Thunderbird supports U2F, the email provider might need to do some work to make it work too, despite them already supporting U2F with webmail. Reading https://bugzilla.mozilla.org/show_bug.cgi?id=1444101 (Enable FIDO U2F for Thunderbird) I get the impression that the person who implemented the support never verified it ever worked with a email account. Instead they tested its U2F conformance using https://u2f.bin.coffee/ and then stated "Google would then need to make sure their login flow accommodates Thunderbird users with U2F tokens." 1. Has anybody actually gotten U2F to work with a Thunderbird Gmail account ? https://landing.google.com/advancedprotection/ 2. How about other email providers such as Fastmail ? My main account is a Fastmail IMAP account and I would like to make it more secure using U2F. But I don't want to buy a Yubico U2F device (I would actually need two, one as a backup) until its clearer whether it might work. I have asked in the Fastmail support forum whether it works but I suspect that if I get any answer, they'll suggest I ask Mozilla.