When an email is unable to deliver to the recipient, AthletaDesk will alert you with a bell icon in the upper-right corner of your account.

https://cdn.elev.io/file/uploads/o-rXyrlr_74HTiJ5rGFCx7KCn6hRsKqDZkdWcAduyzE/XKQ1gGLoyyWGR7Ry4JlVHsfK1fccucITpVK8KOpqpZo/ad email notif-ZoE.png

When clicked on, the "Notification Center" will provide detail on which email address was unable to receive your message.

https://cdn.elev.io/file/uploads/o-rXyrlr_74HTiJ5rGFCx7KCn6hRsKqDZkdWcAduyzE/nKd0446oUfTWZWiqY7toGntdEJDj8Bx0x44lendoU4U/notif centre ad screenshot-gHA.png

When clicking on the blue "Zoom" button to the left of the entry, the pop-up will provide a message from the mail system explaining why the email was unable to send. In most cases, this is due to an incorrect email address, a typo in the email address or the recipient's mailbox is full.

https://cdn.elev.io/file/uploads/o-rXyrlr_74HTiJ5rGFCx7KCn6hRsKqDZkdWcAduyzE/6p8sHSaGtdFlmNYtsxbpohG9QBknuWGcndL28-G70mI/undeliverable email ad-3ts.png