Why won't my iPhone save my updated email password

One of my pop email accounts was compromised and I changed the incoming and outgoing password. The revised settings work on my iMAC but are not being passed on my iPhone. I am able to successfully change the revised password for the pop incoming and outgoing servers but then when I check email I receive an error message. When I go back into mail account settings it appears that the original password is still listed and the revised password was not saved.