Well, I should think that asking the question would be OK on an unsecured circuit.
But on the other hand, if the SECSTATE should answer over the same circuit and give details about her personal schedule, then the info probably should be classified and encrypted, due to the potential for a terrorist, an enemy agent or a plain old-fashioned kidnapper to track and attack her during the lunch hour.
But the original question was: Is everything that is sent to the Secretary of State classified by default?
And the answer is "No, not everything that is sent is classified by default."