37 CFR § 2.23 - Requirement to correspond electronically with the Office and duty to monitor status.
(a) Unless stated otherwise in this chapter, all trademark correspondence must be submitted through TEAS.
(b) Applicants, registrants, and parties to a proceeding must provide and maintain a valid email address for correspondence.
(c) Except for submissions under §§ 2.91, 2.93, and 2.149, if the applicant or registrant is a national of a country that has acceded to the Trademark Law Treaty, but not to the Singapore Treaty on the Law of Trademarks, the requirements of paragraphs (a) and (b) of this section do not apply.
(d) Notices issued or actions taken by the USPTO are displayed in the USPTO's publicly available electronic systems. Applicants and registrants are responsible for monitoring the status of their applications and registrations in the USPTO's electronic systems during the following time periods:
(1) At least every six months between the filing date of the application and issuance of a registration;
(2) After filing an affidavit of use or excusable nonuse under section 8 or section 71 of the Act, or a renewal application under section 9 of the Act, at least every six months until the registrant receives notice that the affidavit or renewal application has been accepted; and
(3) After notice of the institution of an expungement or reexamination proceeding under § 2.92, at least every three months until the registrant receives a notice of termination under § 2.94.