Section 16. For the purpose of this chapter, an insurance-support organization transacting business outside the commonwealth which has an effect on a person residing in the commonwealth shall be deemed to have appointed the commissioner to accept service of process on its behalf; provided, however, that the commissioner causes a copy of such service to be mailed forthwith by registered mail to the insurance-support organization at its last known principal place of business. The return postcard receipt for such mailing shall be sufficient proof that the same was properly mailed by the commissioner.