A (rather aged) friend uses Mozilla Thunderbird as mail client for her Gmail imap account. It is not likely that she will ever switch (that would be my solution). Auto update is on and the latest update has broken something, so when she clicks on a message in the inbox instead of opening it in a view window, it opens an edit window with her own email address instead of that of the sender and it displays an error banner saying "A unique identity matching the From address was not found (...) " I tried uninstalling and re-installing, deleting the profile and making a new one but that makes no visible difference.