If a document is filed by mailing, and if the date of mailing is shown by a postmark affixed by the United States Postal Service or by other proof from the Postal Service, the date of filing will be deemed to be the date of mailing. If the document is mailed but it is postmarked by any other means (such as a private postage meter, the internet, or a Postal Service self-service kiosk), the document will be deemed filed on the date of its receipt by the clerk's office.
Alaska R. App. P. 502.1