This directory contains the repository of all versions of BSD UNIX Sendmail that have ever been shipped with BSD UNIX releases. It includes versions 4.12, 5.52, 5.60, 5.61, 5.61.1.1, 5.64, and 5.67. 5.52 is really 5.52, even though its src/Version.c (and hence the SMTP greeting) says 5.51 (whoever built it forgot to update src/Version.c).