Emails classified as "Delayed" are unable to be delivered because the recipient server was unable to be reached, or has been unable to receive the message. The message will attempt to resend the message over the next 68 hours. "Delayed" notifications do not mean that the message has been blocked.
This is usually caused by issues occurring on the recipient server, but can also commonly be caused by misspelled recipient email addresses, full mailbox, rejections from the recipient, or due to bulk emails being sent out.
If your message is urgent, we recommend contacting recipient by an alternative non-email method.
If you are seeing a lot of delayed bulk emails, it would be worth adding additional security to your emails by adding an SPF record to your domain.
If you would like further assistance, please forward the "Message Digest" email, which includes the details of the "Delayed" email in question, to firstname.lastname@example.org