I'm having a stock email problem, slightly different though. It will not let me add an AOL account as an actual AOL account. I have to add it as an "other" account. Not nearly as annoying as your problem, but you're not the only one having issues with this app.

 

I was having the same problem with the email app and my yahoo account most of last week.
I finally just deleted the email account and then added it again. However, when I tried to add my yahoo account the phone says that the account already exists so I had to use the other pop 3 mail provider and now it works. Definitely strange that this problem is happening.