Installed Tbird 45.2 on new office machine (Win 7). Set up to download Yahoo and gmail accounts. Tbird downloaded messages from both accounts separately and displayed them both in the gmail account. Deleted all accounts, uninstalled Tbird, restarted. When reinstalled and set up Yahoo account, got inbox full error. There were no messages in the inbox but I compacted all inboxes anyway. No effect. Re-establishing gmail accounts works fine. Yahoo inbox is very large, but my home machine running Tbird has no problem with it. Deleted profile files, restarted. Tbird correctly regenerated the files, but repeated the error.