37 CFR § 2.195 - Filing date of trademark correspondence.
The filing date of trademark correspondence is determined as follows:
(a) Electronic submissions. The filing date of an electronic submission is the date the Office receives the submission, based on Eastern Time, regardless of whether that date is a Saturday, Sunday, or Federal holiday within the District of Columbia.
(b) Paper correspondence. The filing date of a submission submitted on paper is the date the Office receives the submission, except as follows:
(1) Priority Mail Express®. The filing date of the submission is the date of deposit with the USPS, if filed pursuant to the requirements of § 2.198.
(2) Certificate of mailing. The filing date of the submission is the date of deposit with the USPS, if filed pursuant to the requirements of § 2.197.
(c) Email and facsimile submissions. Email and facsimile submissions are not permitted and, if submitted, will not be accorded a date of receipt.
(d) Interruptions in USPS. If the Director designates a postal service interruption or emergency within the meaning of 35 U.S.C. 21(a), any person attempting to file correspondence by Priority Mail Express® Post Office to Addressee service who was unable to deposit the correspondence with the USPS due to the interruption or emergency may petition the Director to consider such correspondence as filed on a particular date in the Office. The petition must:
(1) Be filed promptly after the ending of the designated interruption or emergency;
(2) Include the original correspondence or a copy of the original correspondence; and
(3) Include a statement that the correspondence would have been deposited with the USPS on the requested filing date but for the designated interruption or emergency in Priority Mail Express® service; and that the correspondence attached to the petition is the original correspondence or a true copy of the correspondence originally attempted to be deposited as Priority Mail Express® on the requested filing date.