Do you have an @icloud.com email address that you use with your iCloud account? Although the email address may be unique but whilst using this email, there comes some consequences, the most critical being that if your iCloud account’s storage is full then you will no longer receive emails at your @icloud.com email address.
You will not receive any emails on your @icloud.com email as long as your account’s iCloud storage is full. While your iCloud storage is full, you won’t receive any notification or alert about any emails missing or not delivering to your @icloud.com email address.
Instead, the person who will be trying to send you an email to your @icloud.com email address will get a bounce-back message which will state that “User over quota: cannot receive new mail.”
You won’t receive any notification or any specific warning that they are unable to receive emails on their email address while they will receive just the regular “iCloud storage full” message which is a common sighting for most of the iOS device users.
This is just a warning for all the users who use an @icloud email address. If your iCloud account is running out of storage then you should consider upgrading your storage plan as to continue receiving emails to your same @icloud.com email address.
If upgrading your storage plan isn’t an option then you should probably think about freeing up the storage in your iCloud account by deleting old backups and useless data that you no longer need in order to continue receiving emails to your @icloud.com email address.