Service shall be made by leaving the original and two copies of both the summons and complaint, and the fee required by section two, article one, chapter fifty-nine of this code, with the secretary of state, or in his office, and said service shall be sufficient upon said nonresident. In the event any such summons and complaint is so served on the secretary of state he shall immediately cause one of the copies of the summons and complaint to be sent by registered or certified mail, return receipt requested, to the employer at the latter's last known or reasonably ascertainable address. The employer's return receipt or, if suchregistered or certified mail is returned to the secretary of state refused by the addressee or for any other reason is undelivered, such mail showing thereon the stamp of the post-office department that delivery has been refused, or other reason for nondelivery, shall be appended to the original summons and complaint, and filed by the secretary of state in the clerk's office of the court from which said process issued.