Yes. Licensees may mail an unloaded handgun to another licensee in customary trade shipments. Handguns may also be mailed to any officer, employee, agent, or watchman who is eligible under 18 U.S.C. 1715 to receive pistols, revolvers, and other firearms capable of being concealed on the person for use in connection with his or her official duties.
However, postal service regulations must be followed. Any person proposing to mail a handgun must file with the postmaster, at the time of mailing, an affidavit signed by the addressee stating that the addressee is qualified to receive the firearm, and the affidavit must bear a certificate stating that the firearm is for the official use of the addressee. See the current Postal Manual for details.
[18 U.S.C. 1715]