Lookup for "500 2.7.9"
This status code indicates a successful delivery or other operation. Any details are simply notes.
Basic Status Code Details (500)
Syntax error, command unrecognized [This may include errors such as command line too long]
Enhanced Status Code Details (2.7.9)
Authentication mechanism is too weak
The selected authentication mechanism is weaker than the server policy permits. Client should retry with a new authentication mechanism.