RBI Governor Raghuram Rajan has received a threatening e-mail following which his security has been stepped up, a top Home Ministry official said here on Thursday. “The said letter was received a few days back. We have taken note of it and the RBI Governor’s security has been beefed up,” Maharashtra’s Additional Chief Secretary (Home) KP Bakshi told PTI here. However, he did not elaborate on the contents of the threatening e-mail.