Lookup for "535 2.7.7"
This status code indicates a successful delivery or other operation. Any details are simply notes.
Basic Status Code Details (535)
Authentication failed due to invalid or insufficient authentication credentials
Enhanced Status Code Details (2.7.7)
Message integrity failure
A transport system otherwise authorized to validate a message was unable to do so because the message was corrupted or altered. This may be useful as a permanent, transient persistent, or successful delivery code.