There will be a time when someone leaves the company and you need to disable his Bugzilla account by putting a comment in “Disable text”. However disabling a user doesn’t prevent his email address to receive further bug email notifications.
A Bugzilla administrator can stop a user from receiving bugmail by clicking the “Bugmail Disabled” checkbox when editing the user account. This is a drastic step best taken only for disabled accounts, as it overrides the user’s individual mail preferences. Alternately, you can add their email address to the data/nomail file (one email address per line). This will override their personal preferences, and they will never be sent mail again.