RHEL: Change MTA to Sendmail

# /etc/init.d/postfix stop
Shutting down postfix:                                     [  OK  ]

This one will fail

# /etc/init.d/sendmail stop
Shutting down sm-client:                                   [FAILED]
Shutting down sendmail:                                    [FAILED]

# alternatives --config mta

There are 2 programs which provide 'mta'.

  Selection    Command
-----------------------------------------------
*  1           /usr/sbin/sendmail.sendmail
 + 2           /usr/sbin/sendmail.postfix

Enter to keep the current selection[+], or type selection number: 1

Turn Postfix auto off, and Sendmail auto on:

# chkconfig --level 345 postfix off
# chkconfig --level 345 sendmail on

Don't forget to turn the sendmail service on once again.