Second problem.  Some of my emails do not appear in Thunderbird but are displayed in the AT&T email reader.  Thunderbird is my primary reader but I have to log on to the AT&T reader to delete emails from their server.  When I log on to delete emails I discover emails that were not displayed in Thunderbird.

Recently, I think after a recent update, I began having a problem with sending emails sent with BCC only addresses. I checked all my settings and they are correct. Forum respondent advised that some systems will not send emails with BCC only addresses; however, I have never had a problem with BCC only addresses until recently. I did try adding an address in the To field with mixed results. Sometimes the email would send and others not. Second problem. Some of my emails do not appear in Thunderbird but are displayed in the AT&T email reader. Thunderbird is my primary reader but I have to log on to the AT&T reader to delete emails from their server. When I log on to delete emails I discover emails that were not displayed in Thunderbird.