Email account password is most easily changed through the control panel.
First log in to control panel using your administrator username and password.
Go to the target email accounts settings by first selecting 'Mail' from the menu on the left and then clicking on the email account name.
In the account editing view fill in the 'Password' and 'Confirm password' fields and confirm by clicking 'OK' button in the bottom of the form.
Note! Do not click on the 'Generate' button below the password input field. The button inserts a randomly generated password to the password fields, so if you already have input the desired password the button will overwrite your input with a randomly generated password.