quoting from /etc/mail/sendmail.conf:
# HANDS_OFF="No"; Binary Do *NOT* touch the configuration
# Set this *ONLY* if you are going to be fully responsible for the entire
# setup of sendmail - the directories, permissions, databases, etc. With
# this variable set to "Yes", nothing will be done for you during updates.
#
# In other words, "The blood be upon your hands" if you set this...
# My ability to help with problems will be greatly reduced !
#
# "Well, a pet peeve of mine is people who directly edit the
# .cf file instead of using the m4 configuration files.
# Don't do it! [laughs] I treat the .cf file as a binary
# file - you should too."
# -- Eric Allman 1999/10/18
# http://www.dotcomeon.com/allman_sendmail_qa.html
#
HANDS_OFF="No";