The problem with this approach is that we don't get the distinctive tone alerts for each account. 
We realized that Yahoo mail was not available and could not be re-established. Went to the VZW store for direction and learned that this problem has exisited for a while. Android phones are not reliably compatible with mail systems other than G.mail. The answer for Yahoo...download the Yahoo mail app. This not only solved the access problem, but we can also see the files set up on the Yahoo system (rather than the "combined inbox" view that we had initially). Why VZW did not tell us that...either on this blog or as a consumer...beats me!
The problem with this approach is that we don't get the distinctive tone alerts for each account.
I found how to assign custom tones for each of your yahoo accounts.
From the yahoo app go to: Tools> Settings> choose the account you want to assign the custom tone> Notifications Settings> Choose Sound> Select tone> then click Done.
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