To change your password to Roundcube Webmail with thexyzserver.com please follow these directions below:
Login to Roundcube Webmail here: https://webmail.thexyzserver.com
If you have a dedicated server, you may have access to a URL on your own domain, this would be webmail.yourdomain.com
Select Settings at the top right of the screen.
Select Password from the menu on the left. Enter your current password and then enter your new password twice.
Be sure to include a mix of lowercase, uppercase numbers and special characters.
Click to save and you will see a confirmation message in the bottom left of screen.