Thanks for your reply Chris. Sorry I was not clearer. The device works fine, and starts up properly as it always has. The problem, which never appeared before, occurs when you click on the "Email" icon on the Main Screen. (The 'Home Page' I was referring to was the browser home page, which, oddly enough seems to be okay now.)
The Yahoo e-mail screen comes up, with old messages still there from when I last used it weeks ago. But then a window appears which says "Cannot Get Mail. The connection to the server failed". I click the included "Okay" button, the window disappears, then reappears. After a couple of tries, it stops reappearing. I'm left with just those old messages.
My newer iPad which I use regularly has no problem accessing the same server at the same time.
Strangely enough, if I go to Yahoo using the browser on this old iPad, I can sign in and access the mail account and any new messages. But I cannot get there using the "Email" icon on the iPad's main screen.