37 CFR § 2.18 - Correspondence, with whom held.
(a) Establishing the correspondent. The Office will send correspondence as follows:
(1) If the applicant, registrant, or party to a proceeding is not represented by an attorney qualified to practice before the Office under § 11.14(a) of this chapter, the Office will send correspondence to the applicant, registrant, or party to the proceeding.
(2) If an attorney is recognized as a representative pursuant to § 2.17(b)(1), the Office will correspond only with that attorney. A request to change the correspondence address does not revoke a power of attorney. Except for service of a cancellation petition, the Office will not correspond directly with the applicant, registrant, or a party to a proceeding, or with another attorney from a different firm, unless:
(ii) The attorney has been suspended or excluded from practicing in trademark matters before the USPTO; or
(iii) Recognition of the attorney has ended pursuant to § 2.17(g).
(b) Ex parte matters. Only one correspondence address may be designated in an ex parte matter.
(c) Maintaining and changing the correspondence addresses. The applicant, registrant, or party to a proceeding must maintain current and accurate correspondence addresses, as required by § 2.23, for itself and its attorney, if one is designated. If any of these addresses change, a request to change the address, signed in accordance with § 2.193(e)(9), must be promptly filed.
(d) Post registration filings under sections 7, 8, 9, 12(c), 15, and 71 of the Act. Even if there is no new power of attorney or written request to change the correspondence address, the Office will change the correspondence address upon the examination of an affidavit under section 8, 12(c), 15, or 71 of the Act, renewal application under section 9 of the Act, or request for amendment or correction under section 7 of the Act, if a new address is provided, in accordance with paragraph (a) of this section.