Disabling Expiration Notifications
If you have disabled auto-renewal on the domain you want to let expire, simply toggle the checkbox which appears on the card showing the registration status of your domain management page of non-auto-renewing domains.

Be careful with this feature. You will not get any notifications of expiration of domains for which you disable these notifications.
Have more questions?
If you have any questions about disabling expiration notifications, just contact support, and we will be happy to help.