Sendmail smart relay with TLS and plain auth

Instructions on how I set up sendmail smart relay with TLS and plain authenetication on CentOS 6.

First, make sure you have enough installed :

yum -y install ca-certificates sendmail sendmail-cf

Create /etc/mail/authinfo:

AuthInfo:YOUR.HOST.COM    "U:YOUR-USER@YOUR.HOST.COM" "I:YOUR-USER" "P:YOUR-PASSWORD" "M:LOGIN PLAIN"

Replace YOUR.HOST.COM, YOUR-USER and YOUR-PASSWORD with the correct stuff. LOGIN PLAIN stays as-is if you are using plaintext logins. Make sure to chmod 0600 this file.

Add the following to /etc/mail/sendmail.mc, making sure you use m4's dumbass `quotation' style

define(`SMART_HOST', `YOUR.HOST.COM')dnl
define(`RELAY_MAILER',`esmtp')dnl
define(`RELAY_MAILER_ARGS', `TCP $h 587')dnl
FEATURE(`authinfo')dnl
define(`confCACERT_PATH', `/etc/pki/tls/certs')dnl
define(`confCACERT', `/etc/pki/tls/certs/ca-bundle.crt')dnl

Note that the above is TCP port 587, which you might need to change.

Finally you restart sendmail and test as you normally woudl.

chmod 0600 /etc/mail/authinfo
service sendmail restart
echo "Testing" | mail -s "Test 1" somebody@example.com
tail -F /var/log/maillog