To change your password, you need to log onto the web based email client. This is a website where you can get to your email. Note that if you are using Outlook or Outlook Express in POP3 mode, then your emails that you have already downloaded may no longer be on the server. Regardless, logging into the web mail client is the way you need to change your password.
The web mail client is at http://mail.yourdomain.com/mail where “yourdomain” is the name if your domain name. You will see the following login page.

Enter your user name and your password and press Login. Note that your user name is your FULL email address.

On the next page, you need to click “Settings” at the top of the screen. Then click ‘Accounts’, then click ‘Modify’. This will bring you to a page where you can change your password.
When you are finished, press ‘Save Changes’.
You will now need to go back into Outlook and change the password that you may have saved in the account settings.