Open Thunderbird's password vault and delete the entries for the affected accounts. When you check for new messages or try to send one, Thunderbird will ask for the password afresh. Enter the correct password and see how things go. I highly doubt data transmission speed is the issue here.

Did nothing problem still happens. Not always but often. About every once out of 3-5 times I retrieve the email.

one thing most people using windows have that affects mail clients and not webmail is an anti virus. THey are rather a sad thing when it comes to speed and have other issues as well, but disabling any mail scanning of encrypted connection scanning can often work a treat.

I do not use any thing special, only Microsoft Windows 10 antivirus, malware and such. I do not believe that the downloads are actively scanned. I am still of the belief that this is a timing problem and If I could add a delay between Thunderbird sending the user Id and the password it might fix this problem. I do not know what has recently changed. I believe, either Thunderbird, Earthlink or the internet, is causing this problem, or the combination of. I have 3 windows devices and 3 Android tablets and phone accessing this Earthlink account. I do not use Thunderbird on anything but this, my main system. But it is also the only one I am having problems with. It is on this system that I have used this email reader and server for over 15 years and keep all the email archives. The hardware has changed and been upgraded, but not for over 5 years. The software has always been Windows, Earthlink mail server and Thunderbird. I like Thunderbird and I like the service that Earthlink has provided over the years.

I do not use any thing special, only Microsoft Windows 10 antivirus, malware and such. I do not believe that the downloads are actively scanned.

You don't have to believe it for it to be true. Any security program worth its salt is scanning network communications and other actions performed by programs, especially a mail client like Thunderbird. Unfortunately, this nature of security programs has been the bane of Thunderbird's woes for ages, so you should add Thunderbird's profile folder to your AV's exclusions and add Thunderbird as a trusted application to make sure its normal working is not interfered with.

I am still of the belief that this is a timing problem and If I could add a delay between Thunderbird sending the user Id and the password it might fix this problem.

Your belief is misguided because it makes the assumption that Thunderbird doesn't wait for the server to respond during the authentication routine, so it just keeps bombarding the mail server with transmissions of the login credentials to a point of rendering the server incapable of responding. That would pretty much qualify as a denial of service attack, making Thunderbird a malicious program! That's just not how Thunderbird interacts with mail servers. There is no delay to set in Thunderbird AFAIK, but if you insist, you can slow down Thunderbird's transmission speed by limiting your internet speed using the bandwidth controls of your router.

You seem to have misunderstood what I am asking. I am fully aware that this is a handshake deal with a prompt and response arrangement. But normally it is a human responding. A human typing a response. This takes time. More than seconds. Software can do this in fractions of a second. I am saying that Earthlink may not be prepared for a millisecond response of the password, which if produced by a human, the reply would happen in seconds. I am merely looking for a more human reaction of the software. A delay of a second or two from the password prompt to the sending of the password. As Earthlink is saying that if their Webmail interface is not having problems it is not our problem.

You can get webmail-like behaviour by opting out of Thunderbird's saving/remembering of passwords. Open Thunderbird's password vault via Preferences > Saved Passwords then delete stored passwords for the affected account. When Thunderbird asks for the password, uncheck the option to remember the password so that it always prompts you to enter the password instead of automatically using the one stored in the password vault. It's exactly the "human typing a response" experience you're talking about. This is the closest you'll get to adding a delay to the password transmission.

Ok I give up. I did as you suggested and deleted the passwords for the 2 Earthlink accounts that I access with Thunderbird and still got a failure on both accounts when I entered the password when Thunderbird prompted for it.

I also entered "C:\Program Files (x86)\Mozilla Thunderbird\thunderbird.exe" as an exclusion for scanning in Microsoft Defender Antivirus Scans as well as turned off the Microsoft Defender Real time Protection. I still got failures.

So it does not seem to be related to timing as I thought and also not related to Antivirus protection.

What next do you suggest.