5.7.0

Message Not Delivered: unknown security or policy concern

The message could not be delivered because the message has caused a security concern, but it is not clear what caused the problem.

Fixes

Retry the email message see if it was a one-time problem or if the same error occurs.

Otherwise, contact the sender's email support team as the email system may have a security issue.

5.7.0: Official Definition

5.X.X

[RFC3463] (Standards Track) from the The Internet Engineering Task Force (IETF) definition for codes that start with 5.X.X:

A permanent failure is one which is not likely to be resolved by resending the message in the current form. Some change to the message or the destination must be made for successful delivery.

X.7.0

[RFC3463] (Standards Track) from the The Internet Engineering Task Force (IETF) definition for codes that end with X.7.0:

Something related to security caused the message to be returned, and the problem cannot be well expressed with any of the other provided detail codes. This status code may also be used when the condition cannot be further described because of security policies in force.