Delays in Marketing Cloud Identity Verification Emails

If a verification email is received outside of this 10 minute window, the message may have been deferred or held by the recipient email service provider (ESP).  Mimecast, a common ESP, may greylist the Marketing Cloud notification account. It is possible to confirm if your ESP is Mimecast by utilizing the following website and entering your base domain, for example test@example.com would enter example.com in the Domain Intelligence field within the following website:

https://xnnd.com/dni.cgi?d=

MX records at *.mimecast.com indicate mail hosted on Mimecast.

To resolve greylisting issues, see Mimecast's external documentation on how to make administrative changes to alleviate this:

https://mimecastsupport.zendesk.com/hc/en-us/articles/34000390156947-Policies-Configuring-Permitted-Senders-Policy

https://mimecastsupport.zendesk.com/hc/en-us/articles/34000704345363-Policies-Auto-Allow-Creation-Policy-Configuration

If the recipient email address is not hosted by Mimecast, allowlist the following sending IP addresses:

13.111.157.253
13.111.171.210
13.111.171.211