47 CFR 13.10: Licensee address.

In accordance with § 1.923 of this chapter, all applicants (except applicants for a Restricted Radiotelephone Operator Permit or a Restricted Radiotelephone Operator Permit-Limited Use) must specify an email address where the applicant can receive electronic correspondence. Suspension of the operator license may result when correspondence from the FCC is returned as undeliverable because the applicant failed to provide the correct email address.