I'm having the same issue on my wife's android phone. Our provider changed his smtp address and I can't update the account settings on her phone.
On my I phone I noticed that for my gmail account (in outlook) I can't change the settings. But on my cox account I can see an "edit login information" option where I can change the SMTP info.
The difference between the two accounts is that for the google account I let my phone setup the account automatically but for my cox account I changed the SMTP settings manually from the beginning.
So to me it looks like that if the email account was setup automatically you can't change the info anymore. But if you had setup the account manually to start with, then you can change the settings.
So I'm afraid I will have to delete the account for my wife and create a new account.

