I would guess that you have at least one other account, one that you have left dormant and which has that email address listed in the account information. For whatever reason they didn't see fit to include the account ID in those messages, which wasn't very helpful.
When I got that message I opened up my account list (in PasswordSafe) and then signed in to all of my old Yahoo accounts in turn. Except for a couple which had gone so dormant that the ID was said to be available, which I left abandoned.
At 06:15 PM 6/14/2013, you wrote:
> I got the email today in my alternate account saying that my account
> would be closed if I didn't log in by July 15.
> I use Yahoo Mail nearly every day from both my work and home computer.
> I have to login again every 2 weeks.
> So why did I get that email? How do I make sure that they don't close
> my account on 7/15?