Stopped working with Apple Mail and iPhone

Stopped working with Apple Mail and iPhone

Last week my IMAP account stopped working suddenly with Apple Mail and my iPhone, it says I have the incorrect log in details.  I have since changed my info many times and I still can only get the Mail web interface to work. Even though I have updated my PW many times and I know I am typing it correctly, neither Apple Mail or the iPhone will recognize the account. If I can not get this resolved, I am going to have to change my email provider again.