First of all, install postfix and remove sendmail: <br>
    {{Code|yum -y install postfix<br>    yum -y remove sendmail<br>}}
Openssl and openssl-perl are needed to generate certificates and create SSL connections to GMail<br>
Openssl should be installed already, but to be sure: <br>
    {{Code|yum -y install openssl openssl-perl<br>}}
A Certificate Authority is needed to create the necessary certificates. You can skip the next paragraph if you already have one:<br>
    {{Code|cd /etc/pki/tls/misc<br>    ./CA.pl –newca<br>}}
*You will be prompted for the file name, hit enter to create a new CA.
Now a key that is sent to GMail to start the SSL encryption will be created: <br>
    {{Code|cd /etc/pki/tls<br>    mkdir gmail_relay<br>    cd gmail_relay<br>    openssl genrsa -out server.key 1024<br>    openssl req -new -key server.key -out server.csr<br>}
You will be prompted for country etc. like when creating the CA. Enter the same values. <br>
As Common Name, now enter the name of your server, FQDN or not, your choice. <br>
    {{Code|openssl ca -out server.pem -infiles server.csr<br>}
You will need to enter your passphrase again at this point.<br>
When asked if you want to sign the key, answer  yes, same when asked if to commit it.
Add the following to the bottom of the file /etc/postfix/main.cf. 
You do not need to change anything else in it, as the last setting for any option is the one that is saved.
   {{Text|Text=#### GMail SSL SMTP Relay  relayhost <nowiki>= </nowiki> [smtp.gmail.com]:587
  #auth
  smtp_sasl_auth_enable<nowiki>=</nowiki>yes  smtp_sasl_password_maps <nowiki>= </nowiki> hash:/etc/postfix/sasl_passwd
  #tls
  smtp_use_tls <nowiki>= </nowiki> yes  smtp_sasl_security_options <nowiki>= </nowiki> noanonymous  smtp_sasl_tls_security_options <nowiki>= </nowiki> noanonymous  smtp_tls_note_starttls_offer <nowiki>= </nowiki> yes  tls_random_source <nowiki>= </nowiki> dev:/dev/urandom  smtp_tls_scert_verifydepth <nowiki>= </nowiki> 5  smtp_tls_key_file<nowiki>=</nowiki>/etc/pki/tls/gmail_relay/server.key  smtp_tls_cert_file<nowiki>=</nowiki>/etc/pki/tls/gmail_relay/server.pem  smtpd_tls_ask_ccert <nowiki>= </nowiki> yes  smtpd_tls_req_ccert <nowiki>=</nowiki>no  smtp_tls_enforce_peername <nowiki>= no<br/nowiki>no}}
Create /etc/postfix/sasl_passwd file with your GMail login credentials that looks like below:
  {{Text|Text=gmail-smtp.l.google.com user@gmail.com:password<br>  smtp.gmail.com user@gmail.com:password<br>}}
Obviously, you need to change ''user'' to your username and ''password'' to your gmail password. <br>
Create the password  database: <br>
    {{Code|postmap hash:/etc/postfix/sasl_passwd}}
    Protect the files with your GMail login data:
    {{Code|chmod 600 /etc/postfix/sasl_passwd    chmod 600 /etc/postfix/sasl_passwd.db    chown postfix /etc/postfix/sasl_passwd    chown postfix /etc/postfix/sasl_passwd.db<br>}}
Restart Postfix
    {{Code|/etc/init.d/postfix restart}}
Now try sending a mail, it should reach your gmail account.