Section 3D. Application for registration of a motor vehicle or trailer or for a license to operate motor vehicles shall constitute and irrevocably appoint, in case the certificate of registration or license applied for is issued, the registrar or his successor in office the true and lawful attorney of the applicant, upon whom may be served all lawful processes in any action or proceeding against him, or his executor or administrator, growing out of any accident or collision in which he or his agent may be involved while operating a motor vehicle within the commonwealth during the period covered by the certificate of registration or by the license as the case may be, and any process against him which is so served shall, if he is notified of such service as hereinafter provided, be of the same legal force and validity as if served on him personally and the mailing by the registrar of a copy of such process to him at his last address as appearing on the registrar's records shall be sufficient notice to him of such service. Service of such process shall be made by leaving duplicate copies thereof with a fee to be determined annually by the commissioner of administration under the provision of section three B of chapter seven in the hands of the registrar, or in his office, and the registrar shall forthwith send one of said copies by mail, postage prepaid, addressed to the defendant at his last address as appearing on the registrar's records; and an affidavit of the registrar, or of any person authorized by him to send such copy, that such copy has been so mailed shall be prima facie evidence thereof. One of the duplicates of such process, certified by the registrar as having been served upon him, shall be sufficient evidence of service upon him under said power of attorney. The court in which the action is pending may order such continuances as may be necessary to afford the defendant reasonable opportunity to defend the action.