IF the account is still active on old computer and you use WIndows, these steps generally work: - exit tb on old computer - copy profile (normally c:\users\<yourid>\appdata\roaming\thunderbird ) to external media - install tb on new computer and exit - copy the backed up thunderbird folder to c:\users\<yourid>\appdata\roaming to overwrite the default thunderbird folder created by the install. - start tb on new pc.