Step 1
Check if sendmail is compiled with TLS (for encryption) and SASL (for authentication). This is the command to use to check it.
#/usr/sbin/sendmail -d0.1 -bv root
You must read something like “Compiled with…STARTTLS”
Att.: If you’ve installed sendmail using yum, TLS support is present !
Step 2
Install all these packages
# yum install sendmail sendmail-cf cyrus-sasl-plain cyrus-sasl-md5
Step 3
Create certificates
# cd /etc/pki/tls/certs # make sendmail.pem