My short answer is yes :D. It could be either. It also could be something else. The trick is to isolate facts, then define a problem based on those.

You know is that Embarq web mail is slow.
You know other web mails are not slow.

These facts suggest the issue is not a general one with your PC, but they do not rule it out.

On the other hand (sorry) typing in a HTML input box should not be echoing chanracters to the server depending on how it is written. I do not use their service so I do not know.

A key fact to know would be: Is Embarq slow on MY account from a different PC (rec center or neighbor)?

If it is slow there you have enough facts to know your PC is OK. That does not fix it but is great news. Now you can chat with Embarq.

That said, if you do not use MalwareBytes, grab it off the net and run it no matter what.

Not sure why I thought of this thread, but...
 

I was curious whatever happened with this issue? Did things work? Did you figure out why?

My centurylink email is working fine. Could be your personal connection. Good luck.

Perfect timing AJ. Started sending out emails last night and everything worked fine. I tested it last week and it was still miserable. Be darned if I can figure out what the problem is/was. So, it works for now and I still have no clue what the problem is, but I'll take what I can get.