Section 34K. No power of attorney in connection with the cancellation of a motor vehicle liability policy as defined in section thirty-four A shall be exercised until ten days' notice has been given to the policyholder by registered or certified mail, return receipt requested, by the person or corporation exercising the power of attorney. Notice to the insurance company of the cancellation of such a policy by a person or corporation exercising the power of attorney shall be accompanied by a statement of compliance with this section, and the insurance company may rely upon such statement.