Question

Why is my phishing email delayed when it was not delayed earlier?

Answer

Your Phishing emails could be deferred if you are utilizing Exchange Online Protection (EOP) . Deferred means that the recipient's mail server has temporarily refused delivery of an email. If this occurs, we will attempt to send emails for up to 72 hours until the email is delivered. Normally, it takes between a few minutes to a few hours until the email is delivered.

The most common reason for an email deferral is too many emails being sent over a given time frame to a particular email service provider. This is typically addressed by creating a connector in the EAC of Exchange Online (Office 365) to allow the emails from our Sending IPs into the system and bypassing the IP Throttling imposed at that level.   

Please review the Awareness] Safelisting in Office 365  guide for more information.