Today i will show how to send an emails from CentOS using a GMAIL account. For this, we will use mailx and ssmtp.

Go to Gmail and enable this (ACCOUNT):

1. Disable POSTFIX (You can remove, i choose disable)

	root@hostname]# service postfix stop ; chkconfig postfix off

2. Install SSMTP and MailX

 [root@hostname]# yum install mailx ssmtp -y 

in centos 7 i needed install manually: http://pkgs.org/download/ssmtp (centos6)

3. Configure SSMTP /etc/ssmtp/ssmtp.conf file to looks like

root=YOUREMAIL@gmail.com
mailhub=smtp.gmail.com:587
rewriteDomain=gmail.com
hostname=YOURMACHINEHOSTNAME;
UseTLS=Yes
UseSTARTTLS=Yes
AuthUser=YOUREMAIL@gmail.com
AuthPass=YOUR PASSWORD;
FromLineOverride=YES
# This solved if you get a ssmtp: Cannot open smtp.gmail.com:587 when try to send an email
# if you enabled uncommenting DEBUG=Yes line and your /var/log/maillog show
# SSL not working: certificate verify failed (20) Uncomment the following line but first VERIFY FILE EXISTS
TLS_CA_File=/etc/pki/tls/certs/ca-bundle.crt
 #DEBUG=Yes

4. Configure SSMTP /etc/ssmtp/revaliases file to looks like

	root:YOUREMAIL@gmail.com:smtp.gmail.com:587 

5. Configure Alternatives (command mail)

	[root@hostname]# alternatives --config mta 

There are 2 programs which provide ‘mta’.

  Selection    Command
-----------------------------------------------
+  1          /usr/sbin/sendmail.postfix
* 2           /usr/sbin/sendmail.ssmtp
 

Enter to keep the current selection[+], or type selection number: 2 (press ENTER)

6. Test Email

	 [root@hostname]# echo Hi from command line | mail youremail@youremailhost.com 

7. Allow more users to send emails using mail

If you want to allow to more users to send emails using it, just add user to the mail group

	[root@hostname]# gpasswd -a USER mail 

and add a line to the /etc/ssmtp/revaliases

 USER:YOUR EMAIL@gmail.com:smtp.gmail.com:587