37 CFR § 2.18 - Correspondence, with whom held.
(a) Establishing the correspondent. The Office will send correspondence as follows:
(1) If an attorney is not recognized as a representative pursuant to § 2.17(b)(1), 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, except as set forth in paragraphs (a)(2)(i) through (iv) of this section. A request to change the correspondence address does not revoke a power of attorney. The Office will not correspond with another attorney from a different firm and, except for service of a cancellation petition and notices of institution of expungement or reexamination proceedings, will not correspond directly with the applicant, registrant, or a party to a proceeding, unless:
(i) The applicant or registrant files a revocation of the power of attorney under § 2.19(a) and/or a new power of attorney that meets the requirements of § 2.17(c);
(ii) The attorney has been suspended or excluded from practicing in trademark matters before the USPTO;
(iii) Recognition of the attorney has ended pursuant to § 2.17(g); or
(iv) The attorney has been falsely, fraudulently, or mistakenly designated under § 2.17(b)(4).
(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.