How can Moodle administrators stop users changing their email address to a mailbox that is full, or no longer active?If you are an organisation that manually creates accounts for your users (or you use Email-based self registration) you can head over to:
Admin > Plugins > Authentication > Manual accounts / Email-based self registration
In earlier versions of Moodle these would be found under:
Admin > Users > Authentication > ...
Many administrators gloss over this page, but it’s useful in that it allows you to lock fields against further changes. Obviously users cannot change their username, so that isn’t an option here, although some password policy settings are available for manual accounts.
However, many other user profile fields can be changed from Unlocked, to Locked.
If you make this change on the Email address field for example, then users will not be permitted to change the email address from their user profile.
Problem solved !