See: Section I, Rule #2 "Written Proof:"
2. Written Proof: Except in cases where the rules of Section IV apply, proof of two-way communication (contacts) must be submitted directly to ARRL HQ for all DXCC credits claimed. Photocopies and electronically transmitted confirmations (including, but not limited to fax and email) are not currently acceptable for DXCC purposes. Exception: Confirmations created and delivered by ARRL’s Logbook of the World program are acceptable for DXCC credit.