(a) Any interested party may offer evidence that he has mailed the document or letter five days prior to the expiration of the time limit. Except in cases where surface mail normally arrives at its destination within two days of mailing, or where no airmail service is available, such evidence may be offered only if the mailing was by airmail. In any case, evidence may be offered only if the mailing was by mail registered by the postal authorities.
(b) If the mailing, in accordance with paragraph (a), of a document or letter is proven to the satisfaction of the national Office or intergovernmental organization which is the addressee, delay in arrival shall be excused, or, if the document or letter is lost in the mail, substitution for it of a new copy shall be permitted, provided that the interested party proves to the satisfaction of the said Office or organization that the document or letter offered in substitution is identical with the document or letter lost.
(c) In the cases provided for in paragraph (b), evidence of mailing within the prescribed time limit, and, where the document or letter was lost, the substitute document or letter as well as the evidence concerning its identity with the document or letter lost shall be submitted within one month after the date on which the interested party noticed—or with due diligence should have noticed—the delay or the loss, and in no case later than six months after the expiration of the time limit applicable in the given case.
(d) Any national Office or intergovernmental organization which has notified the International Bureau that it will do so shall, where a delivery service other than the postal authorities is used to mail a document or letter, apply the provisions of paragraphs (a) to (c) as if the delivery service was a postal authority. In such a case, the last sentence of paragraph (a) shall not apply but evidence may be offered only if details of the mailing were recorded by the delivery service at the time of mailing. The notification may contain an indication that it applies only to mailings using specified delivery services or delivery services which satisfy specified criteria. The International Bureau shall publish the information so notified in the Gazette.
(e) Any national Office or intergovernmental organization may proceed under paragraph (d):
(i) even if, where applicable, the delivery service used was not one of those specified, or did not satisfy the criteria specified, in the relevant notification under paragraph (d), or
(ii) even if that Office or organization has not sent to the International Bureau a notification under paragraph (d).