Lookup for "552 4.7.5"
Temporary Error - This status code indicates a transient issue and may resolve itself.
Basic Status Code Details (552)
Requested mail action aborted: exceeded storage allocation
Enhanced Status Code Details (4.7.5)
Cryptographic failure
A transport system otherwise authorized to validate or decrypt a message in transport was unable to do so because necessary information such as key was not available or such information was invalid.