More information may help. Do you have more than one email account? If so, does accountsettings>Outgoing SMTP servers show the same number of SMTP servers as accounts? That may not be a cause, but it is not infrequent to have problems posted where there are insufficient SMTP servers for the listed accounts. Thank you.

Thanks for your reply, David. I have just one account, and its SMTP server is the one listed in "Outgoing Server (SMTP) Settings". I should have said that I'm using version 102.13.0 (32-bit), which is stated as up-to-date.

I've never seen this. See if your account pane links to it. The link will be at the bottom of the pane.

In the Account pane, clicking "Outgoing Server (SMTP)" opens a page titled "Outgoing Server (SMTP) Settings". One server is listed: CenturyLink.net - smtp.centurylink.net (Default). The Add and Edit buttons are active, and Remove and Set Default are grayed out. Under "Details of selected server": Description: CenturyLink.net Server Name: smtp.centurylink.net Port: 587 User Name: [my correct email address] Connection Security: STARTTLS

This issue seems to have solved itself. I tried to send a message this morning, and, finally, was prompted for my SMTP server password. When I supplied it, the message was sent successfully. Thunderbird's Saved Logins box now lists the SMTP server as well as the mailbox, both with the correct password.

I've read solutions to problems similar to this, and they said that when you try to send a message, you're prompted for the server password. Didn't happen for me, until this morning. All's well that ends well, I guess. Thanks for your help, David.

I am most pleased this is now resolved for you. :)