1. Except as provided in subsection 2, any appeal to the county board of equalization filed by mail shall be deemed to be filed on the date of the postmark dated by the post office on the envelope in which the appeal was mailed.
2. If the postmarked date on an envelope in which an appeal was mailed is illegible or omitted, the appeal shall be deemed filed on the date it was received by the county board of equalization.
3. A postmark provided by a postage meter, a postage vending machine, any postage purchased through the Internet or any other form of dated postage which is not directly postmarked by the post office does not establish that an appeal is timely filed.