MYMTNMAIL

We are having problems with MYMTNMAIL with our Outlook account. We are unable to send or receive emails and are being asked for a password every time we log in. Our password has remained the same for over 15 years. We have been told to visit an MTN store but we live on a farm, easier said than done. There is no option to reset password and we cannot login through Zimbra either. Can somebody help please. The email was working fine until yesterday morning. Why would we now have issues with a password????