$ sudo apt-get install exim4
			

$ sudo dpkg-reconfigure exim4-config
				

# yum install exim
# chkconfig exim on
# cp /etc/exim/exim.conf{,.original}

			

切换默认MTA

# alternatives --config mta

There are 2 programs which provide 'mta'.

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

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