31 CFR § 363.5 - How do I contact Fiscal Service?
(a) You may use the “Contact Us” feature within TreasuryDirect ® to communicate information to us over a secure Internet connection.
(b) Emails may be sent to: email@example.com. We will reply by e-mail unless you request otherwise. We are not responsible for the security of e-mail messages you may send to us, or replies we may send to you.
(c) Letters should be addressed to the address provided on our web site at http://www.treasurydirect.gov/write.htm.