There are two approaches to installing a new sendmail :
If you choose to run the new sendmail in place of the original, you first need to create and install a new configuration file. The m4 (1) program is used to automate the process of configuration file creation. See Chapter 19, V8 m4 Configuration , for a full description of this process.
If you choose to keep the original and install the new sendmail in parallel (until you can trust it), you may proceed with the installation and defer configuration files until later. Note that this choice presumes that you customized the file locations.
After you have compiled sendmail (and if the configuration file is ready and tested), you can install it as your production version. If you are already running a sendmail and will be overwriting that binary, you will need to kill that version first (see Chapter 4, How to Run sendmail ).
To install sendmail , first type
#./makesendmail -n install
You use 
-n
 to be sure that the installation caused by the 
Makefile
 is in fact correct for your site. A typical such run, for example, might look like this:
install -o root -g kmem -m 6555 sendmail /usr/lib for i in /usr/ucb/newaliases /usr/ucb/mailq; do rm -f $i; \ ln -s /usr/lib/sendmail $i; done install -c -o root -g kmem -m 644 /dev/null \ /etc/sendmail.st install -c -o root -g kmem -m 444 sendmail.hf /usr/lib
Notice that Makefile will not create the queue directory even if it does not exist. If you have never run sendmail on your machine before, you will need to create that queue directory:
#mkdir /var/spool/mqueue#chmod 700 /var/spool/mqueue
See 
Section 34.8.48, QueueDirectory (Q)
 for a description of the  
QueueDirectory
 option and information about how 
sendmail
 locates its queue directory.
If all looks good, you can install sendmail with this command:
#./makesendmail install
But be aware that the new sendmail may not work properly with your old configuration file. See Chapter 19 for guidance in creating configuration files.