Generally port 587 uses STARTTLS. What happens if you make that change. Comparing sending via Web mail and using SMTP only means you know your username and password. But that is the standard line of provider help desks to get you to go away.

I tried the suggestion to use STARTLS keeping the other settings the same and got the following error message:

Add Security Exception

You are about to override how Thunderbird identifies this site. Legitimate banks, stores, amd other public sites will not ask you to do this.

Server location: mail.lumos.net:587 Certificate Status This site attempts to identify itsself wiwth invalid information

Wrong site

This certificate belongs to a different site, which could meana that someone is trying to impersonate this site.

A box which was checked: Permanently store this exception

Two choices: Confirm Security Exception or Cancel

I canceled

Would others suggest I confirm the Security Exception??

Contact the provider and confirm the correct SMTP server setting.

As I said in my question, I already contacted the ISP and they said I was using the correct settings and would not support Thunderbird.

And yet you were using port 587 with no security. You are not going to get anywhere until you have the server settings correct. The first line of help desk staff barely know to answer the phone when it makes a noise. Ask for someone that actually knows something.

The person I was dealing with at the ISP was in charge of solving problems and the same person that problems get referred up to.

You are obviously trying to say something when you said "And yet you were using port 587 with no security" but I can not understand what you are trying to say.

Please add the troubleshooting information to your post To find the Troubleshooting information:

• Open Help (or click on three-line-icon and select Help)
• Choose Troubleshooting Information
• Use the button Copy to clipboard to select all. Do not check box "Include account names"!
• Paste this in your post.

perhaps you as their customer could provider a link to the page on their web site that gives the POP and IMAP server settinfs, such as server name.. Port and connection security. I have googled and Googled. The information is most notable by it's absence, when they give information about Thunderbird it is just a blank space where the information is supposed to be. See https://www.lumosnetworks.com/support/email-upgrades

I can guess, but seriously I should not have to.

I wrote my ISP and pointed out they had left the setting info blank.

I have deleted all info in my outgoing server settings and started fresh. I kept trying different settings until I got one to work. But it looks identical to the one I started with.

Then it stopped working again - so if fussed around with it until it did.

I can not see any differences in the settings I started with and the setting I now have working. I have my notes and they are the same.

A piece of trash? Or maybe the ISP is having problems? I don't know but it is working now. Thanks.