USCIS will send the approved petition to the National Visa Center, which is under the U.S. Department of State (NVC). The NVC collects the fees, the support affidavits, the visa application, all necessary civil documents, photos, police certificates, etc. They review all the forms, schedule the appointment at the U.S. Embassy or Consulate, and mail out the appointment letter. Most of the NVC’s correspondence is now being done by email.