Teaminbox not receiving messages from Apple email accounts

Teaminbox not receiving messages from Apple email accounts

All emails sent from the following Apple email domains to our Teaminbox are failing to be delivered:
  1. mac.com
  2. me.com
  3. icloud.com
I have tested this with our staff Zoho mail accounts, no problems there. These messages are only failing to get delivered to Teaminbox.

Please consider this as urgent.