In federal criminal cases, the general rule is similarly that in-person service is required. This is based on the language of Rule 17 of the Federal Rules of Criminal Procedure, which largely mirrors the language of FRCP 45:
“A marshal, a deputy marshal, or any nonparty who is at least 18 years old may serve a subpoena. The server must deliver a copy of the subpoena to the witness and must tender to the witness one day’s witness-attendance fee and the legal mileage allowance. . . .”