1.) Login to your webmail at (domain.com/webmail or webmail.domain.com)
2.) Click your email address which is located to the upper right position beside logout, then click the password and security..
3.) Then fill-up the new credentials that must be provided (Please secure a backup copy of your password)
4.) Then you're done!
Notice: If you ever forget your password or credentials accidentally, you can seek for help by creating ticket at here our freshdesk ticketing system.