iPhone 5 Mail app constantly pops up "Password Incorrect"
Since ungrading my iPhone 5 to iOS 8 a couple of weeks ago, the mail app constantly pops up a box telling me my password is incorrect and prompts me to enter the correct password. I do this and the mail downloads properly only to get another popup Password Incorrect box soon after. This happens everytime the phone screen goes off and I turn it back on and it sometimes happens WHILE I am using the mail app after having just entered the password.
I have two emails in the app and this problem is only affecting the Exchange account (which is my work email thru a vpn). The other is an IMAP account and doesn't have this problem. Of course, the password in Settings is correct and I have re-entered it multiple times. Interestingly, I can also check this email account on my iPad (also recently updated to iOS 8) and this problem does NOT occur on the iPad. I have deleted the email account from the phone and reinstalled it but to no effect. I have tried searching the internet for a solution but haven't found a good answer specific to my problem. Again, this started immediately after installing iOS 8 on the phone. Please help as this is truly annoying. Thanks,