How to setup E-mail relay

Gmail rejects e-mail from my server.

Solution: E-mail relay through Mandrill (MailChimp service)

1.  Create account with Mandrill (it's free)
2.  Generate some API key on Mandrill website
3.  Setup your Postfix
 yum -y install postfix cyrus-sasl-plain cyrus-sasl-md5

4.  Modify /etc/postfix/main.cf
relayhost = smtp.mandrillapp.com
smtp_sasl_auth_enable=yes
smtp_sasl_password_maps=hash:/etc/postfix/sasl_passwd
smtp_sasl_mechanism_filter = AUTH LOGIN
smtp_sasl_security_options =

5.  Put your credentials in /etc/postfix/sasl_passwd file
smtp.mandrillapp.com yourusername@yourdomain.com:yourapikeyhere

6.  Create sasl db readable by postfix
postmap sasl_passwd
chmod 600 sasl_passwd
chown postfix:postfix sasl_passwd.db


Your maillog should look similar to this:
Mar 15 23:45:05 tm1 postfix/master[29546]: daemon started -- version 2.6.6, configuration /etc/postfix
Mar 15 23:45:41 tm1 postfix/pickup[29548]: 34B98580496: uid=500 from=<user>
Mar 15 23:45:41 tm1 postfix/cleanup[29678]: 34B98580496: message-id=<20150316064541.34B98580496@mail.tagmap.me>
Mar 15 23:45:41 tm1 postfix/qmgr[29549]: 34B98580496: from=<user@mail.tagmap.me>, size=419, nrcpt=1 (queue active)
Mar 15 23:45:42 tm1 postfix/smtp[29680]: 34B98580496: to=<user@gmail.com>, relay=smtp.mandrillapp.com[54.70.134.182]:25, delay=1.3, delays=0.02/0.01/1.1/0.24, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as 5A3F038028A)
Mar 15 23:45:42 tm1 postfix/qmgr[29549]: 34B98580496: removed