37 CFR 41.10: Correspondence addresses.

Except as the Board may otherwise direct,

(a) Appeals. Correspondence in an application or a patent involved in an appeal (subparts B and C of this part) during the period beginning when an appeal docketing notice is issued and ending when a decision has been rendered by the Board, as well as any request for rehearing of a decision by the Board, shall be mailed to: Patent Trial and Appeal Board, United States Patent and Trademark Office, PO Box 1450, Alexandria, Virginia 22313-1450. Notices of appeal, appeal briefs, reply briefs, requests for oral hearing, as well as all other correspondence in an application or a patent involved in an appeal to the Board for which an address is not otherwise specified, should be addressed as set out in § 1.1(a)(1)(i) of this title.

(b) Interferences. Mailed correspondence in interference (subpart D of this part) shall be sent to Mail Stop INTERFERENCE, Patent Trial and Appeal Board, United States Patent and Trademark Office, PO Box 1450, Alexandria, Virginia 22313-1450.

(c) Trial Proceedings. Correspondence in trial proceedings (part 42 of this title) are governed by § 42.6(b) of this title.