Lookup for "535 4.5.6"
Temporary Error - This status code indicates a transient issue and may resolve itself.
Basic Status Code Details (535)
Authentication failed due to invalid or insufficient authentication credentials
Enhanced Status Code Details (4.5.6)
Authentication Exchange line is too long
Authentication failed due to the client sending a [BASE64] response that is longer than the maximum buffer size available for the currently selected SASL mechanism.