Thanks for all the replies. I have checked all of the items listed above, and I still have the problem.
I think I've found a clue, however. I'm now convinced that the problem is related to my "microsoft account". My initial microsoft account was set up using a different laptop (that failed and was sent away for repair) and a different email address (that now is inop due to moving away from the area where that service is available).
The original setup of the microsoft account involved an email address that ended in @centurytel.net. I have attempted to change everything over to an email address ending in @outlook.com.
When I now get into my microsoft account and click the little symbol that looks like a person's outline, I get identity info including the email that ends in @outlook.com. When I get into my outlook.com email (via web browser) and click the little symbol that looks like a person's outline, I get identity info including the old email that ends in centurytel.net.
So far, I have been unable to get that old email out of the identity info of outlook.com.
At this point, I can retrieve email into Thunderbird. I can not send email from Thunderbird. I can get on outlook.com via web browser and send email.
If anyone has ideas of how to correct the identity problem within outlook.com, please let me know.
Thanks again for your help.
Fred
