Sendmail Evolution: 8.10 and Beyond. - Gregory Neil Shapiro; Eric Allman (USENIX ATC, FREENIX Track, 1999)

sendmail 8.13 Companion - The sendmail administrator's reference. - Bryan Costales; George Jansen; Claus Aßmann; Gregory Neil Shapiro (O'Reilly, 2004)

Advice for Safe Handling of Malformed Messages. - Murray S. Kucherawy; Gregory Neil Shapiro; Ned Freed (RFC, 2014)