re :Earthlink webmail does work. Earthlink (2 out of 3 consultants) said I should have the same setting, smtpauth.earthlink.net in both Thunderbird and webmail.

You access webmail using a browser and logon to their website. https://webmail.earthlink.net/wam/login.jsp? You use your email address and your password.

re :How do I remove a colon and 3 extra digits at the end of smtpauth.earthlink.net

In Thunderbird To alter the outgoing server SMTP:

Right click on mail account name in Folder Pane and select 'Settings' Account Settings window opens. In left pane, at the bottom, click on 'Outgoing Server (SMTP)' On the right side it will list your outgoing servers. Select the one you want to alter. It will list the details below. Click on 'Edit' and a new small window opens.

Description: this is a field you can use to help to identify that outgoing server, so you could type something more meaningful eg: Personal or Business or even your email address that uses that server. Edit the server name Server name: smtpauth.earthlink.net click on OK

Now make sure the account is using that server. In left pane, select the account name. Bottom right you will see 'Outgoing Server (SMTP)' Make sure you have selected the correct outgoing server for that account. The Description you entered will help to identify it.

Use the example images below to show exactly what I'm talking about.

click on OK to save and close Account Settings

Exit Thunderbird Wait a few moments for background processes to complete. Start Thunderbird.

Thunderbird says "An account with this name already exists". Please enter a different account name. Its Account Settings window does not look like the images I was sent. Also, the account name now looks correct. I tried to send a test email; it failed. I have a screen shot but I am failing to send it (a .jpg) here. What it says is "You are about to override how Thunderbird identifies this site" and then a warning not to do it.

So your provider has an invalid security certificate or more likely you have an anti virus product that thinks it is a certifying authority in the chain of trust without paying for the audits required.

Click on the certificate error to view the certificate.

What server is it issued for and by whom. Both bits of information are in the certificate, you just have to dig around a little.

re :"You are about to override how Thunderbird identifies this site" and then a warning not to do it. Maybe your Anti-Virus product interfering, so click on the OK.

What Anti-Virus product are you using ?

My antivirus software is Avast. It just happened to ask to update itself and then restart my Windows 10. Now Thunderbird sent my 2 latest test messages (and say they were checked for viruses by Avast). So all appears to be well. I suspect that when Thunderbird showed "SMTPauth.earthlink.net:587" the 587 was an error code. (I said NO, not helpful just to be sure I could post a reply, sorry.)

cnordj said

when Thunderbird showed "SMTPauth.earthlink.net:587" the 587 was an error code.

Nope, for future reference that is connection notation that has been around for more than 30 years. That says Thunderbird was attempting to connect to SMTPauth.earthlink.net on port 587 which would be a correct port of email.

Please also take whatever actions you have toto make sure Avast does not put any text into your emails. That text has the capacity to be used to track your emails and track you for saleable information (avast free is not really free, they make money in there somehow). At the very least you are spamming your correspondents with advertising for Avast. At worst the trackers are passing the emails you send to and the geographic location they are read in to the highest bidder. Best to have the mail leave as you signed it off, not Avast.

I only said I suspected the 587 was an error code. It would have helped to tell me days ago what it meant. Thanks for the warning about Avast. I already have removed its addendum to my emails. Again, sorry to say "not helpful", to be sure I could Reply. I think all is well now.

Again for future reference, unless a moderator closes a thread you have 6 months to comment on it. Solved or not. Note that threads not marked as solved do not appear in search engines, so we are keen to see a solved status. Otherwise we keep repeating ourselves even more than we do now, so thank you for marking the topic solved.