Except as provided in Part 340 and 366 of this Title, service retirement applications, vested retirement applications, disability retirement applications, option election forms and other applications, forms and documents are not filed until the date they are received by the Retirement System. However, such applications, forms and documents will be deemed filed on the date mailed if they are mailed to the Retirement System by the United States Postal Service certified mail, return receipt requested. Notwithstanding this provision, no application, form or document will be deemed filed on its mailing date unless it is actually received by the Retirement System as the result of such mailing.