Configuring sendmail email relay

cd /etc/mail
cp sendmail.cf sendmail.cf.orig
cp sendmail.mc sendmail.mc.orig

mkdir -m 700 -p /etc/mail/auth

touch /etc/mail/auth/auth-info

cd /etc/mail/auth

makemap hash auth-info < auth-info

chmod 0600 /etc/mail/auth/*

Edit /etc/mail/sendmail.mc

define(`SMART_HOST',`smtp.gmail.com')dnl
define(`RELAY_MAILER_ARGS', `TCP $h 587')dnl
define(`ESMTP_MAILER_ARGS', `TCP $h 587')dnl
define(`confAUTH_MECHANISMS', `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
FEATURE(`authinfo',`hash /etc/mail/auth/auth-info')dnl
TRUST_AUTH_MECH(`EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')

Save the file and make the sendmail.cf:

cd /etc/mail

m4 sendmail.mc > sendmail.cf

Restart sendmail service

service sendmail restart

Send test email

echo 'TEST email'| mail -s TEST [email protected]