PGP Encryption is producing a .tmp file at vendor's end

We are using the public key provided by the vendor to encrypt the file being sent to the SFTP using the HCM Extracts vis BIP delivery. When the vendor is decrypting the file using their private key the file is being produced with the .tmp extension and they have to manually rename the file to the source file name to see the contents of the file.

Is there a way that anything can be done from Oracle's end that the file at the vendor side should give the source file name fiel only with proper extension and not the .tmp extension file?