When using cloud service, please apply two-factor authentication as soon as possible: Kaheastmelise autentimise aktiveerimine Microsoft 365-s
NB! Already existing Thunderbird account can be set up to 2FA if You change from Thunderbird Account Settings → Servers tab → password to OAuth2. Same is needed for Outgoing Server.
NB! Thunderbird version must be at least 77. You can download latest version here.