[2] While doing additional graduate studies in Computer Science at the University of Delaware, from 1978 to 1982, he developed MMDF, a message transfer agent program for email servers.
[6] He ran MMDF as a telephone-based ARPANET gateway service for CSNET, which was a forerunner for NSFNET.
[8] By 1974, the year before he obtained his bachelor's degree, he had been listed as an author or credited by name in at least 19 RFCs (351, 352, 462, 498, 539, 560, 577, 581, 585, 615, 645, and 651 through 658), most of which were focused on email or the Telnet protocol for client/server computer terminal communication.
[10][11] After working at MCI from 1983 to 1985, he held networking-related engineering management positions at Ungermann-Bass, The Wollongong Group, and Digital Equipment Corporation, before founding his own consultancy company, Brandenburg InternetWorking, in 1991.
[2] Crocker received the 2004 IEEE Internet Award along with Raymond Tomlinson for their work on the "conceptualization, first implementation, and standardization of networked email".