Who is your email provider?

Cox in Las Vegas.

Lets just check the settings. I ask you to do the following twice, once on each machine and make it clear which works and which does not. If the settings are identical, which I actually think we will see, then it is an external issue, like an anti virus or routing that is the issue. But first to the actual setting you are using.

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 into Notepad
• Delete all the information after the heading "Important Modified Preferences "
• Paste this reduced information in to your post.

Thanks, but where do I find Notepad?

Press the windows key on your keyboard plus R type notepad and press enter.

Or type in into the search box on your start menu.

Will do. I usually use Open Office Writer for Word Processing.

You may be able to use Writer for this job, but it's likely to bring a fair amount of unnecessary code along with the useful text (though very much less than MS Word would bring to the party.) However, when I tested it with Word, it started wrapping the lines in an unhelpful way.

It's a good idea to become familiar with your basic text editing tools. Notepad is the de-facto standard Windows editor. Notepad++ is a useful improvement for more ambitious work. It can understand various writing conventions (html, xml etc) and colour-code them.

Linux folk have nano, gedit, kate, pluma, bluefish etc etc. Oh, and of course vi and emacs.

You don't need a separate editor; you could paste it all into the reply box here and trim it in-situ (though sometime it complains about too many lines or characters.) But when there is a lot of text, a proper text editor makes it a more pleasant job.

Thank you all who made suggestions for my posted problem in which I could not send or receive emails on my NB computer, but I had the last time I used it months ago. Email on my DT works fine.

 In going through all my Account Settings, comparing DT settings to NB settings, I found the problem and solution in Junk Settings > Global Junk Preferences > Security > Passwords and had forgotten (early senility?) that I had changed my DT email password a while ago.
 Now they conform and problem solved.
 Thanks again to all who took the time and made the effort to help.  I sincerely appreciate it.

Vumbo said

Thank you all who made suggestions for my posted problem in which I could not send or receive emails on my NB computer, but I had the last time I used it months ago. Email on my DT works fine.

In going through all my Account Settings, comparing DT settings to NB settings, I found the problem and solution in Junk Settings > Global Junk Preferences > Security > Passwords and had forgotten (early senility?) that I had changed my DT email password a while ago.

Now they conform and problem solved.

Thanks again to all who took the time and made the effort to help. I sincerely appreciate it.