Laravel 5.0 mail() not working in production server with CentOs

I'm using Laravel 5.0 for my project and i have to mail to admin whenever user fill a contact us form. the mail functionality was working fine in my local but when i moved to production server (CENTOS) it was not working.

$sent = Mail::raw('plain text message', function ($message) {
        $message->from('gbhyri@gmail.com', 'bhyri');

        $message->to('gayatri.bhyri@gmail.com', 'gayatri');

        $message->subject('Subject');
});
dd($sent);

I'm getting 0 as output, then have checked with Mail::failures()

array:1 [▼
   0 => "gayatri.bhyri@gmail.com"
]

Getting this one as reason for mail not sent, the TO and FROM emails were working fine.

mail.php

<?php

return [

/*
|--------------------------------------------------------------------------
| Mail Driver
|--------------------------------------------------------------------------
|
| Laravel supports both SMTP and PHP's "mail" function as drivers for the
| sending of e-mail. You may specify which one you're using throughout
| your application here. By default, Laravel is setup for SMTP mail.
|
| Supported: "smtp", "mail", "sendmail", "mailgun", "mandrill", "log"
|
*/

'driver' => 'mail',

/*
|--------------------------------------------------------------------------
| SMTP Host Address
|--------------------------------------------------------------------------
|
| Here you may provide the host address of the SMTP server used by your
| applications. A default option is provided that is compatible with
| the Mailgun mail service which will provide reliable deliveries.
|
*/

'host' => 'smtp.mailgun.org',

/*
|--------------------------------------------------------------------------
| SMTP Host Port
|--------------------------------------------------------------------------
|
| This is the SMTP port used by your application to deliver e-mails to
| users of the application. Like the host we have set this value to
| stay compatible with the Mailgun e-mail application by default.
|
*/

'port' => 587,

/*
|--------------------------------------------------------------------------
| Global "From" Address
|--------------------------------------------------------------------------
|
| You may wish for all e-mails sent by your application to be sent from
| the same address. Here, you may specify a name and address that is
| used globally for all e-mails that are sent by your application.
|
*/

'from' => ['address' => "gbhyri@gmail.com", 'name' => "bhyri"],

/*
|--------------------------------------------------------------------------
| E-Mail Encryption Protocol
|--------------------------------------------------------------------------
|
| Here you may specify the encryption protocol that should be used when
| the application send e-mail messages. A sensible default using the
| transport layer security protocol should provide great security.
|
*/

'encryption' => 'tls',

/*
|--------------------------------------------------------------------------
| SMTP Server Username
|--------------------------------------------------------------------------
|
| If your SMTP server requires a username for authentication, you should
| set it here. This will get used to authenticate with your server on
| connection. You may also set the "password" value below this one.
|
*/

'username' => null,

/*
|--------------------------------------------------------------------------
| SMTP Server Password
|--------------------------------------------------------------------------
|
| Here you may set the password required by your SMTP server to send out
| messages from your application. This will be given to the server on
| connection so that the application will be able to send messages.
|
*/

'password' => null,

/*
|--------------------------------------------------------------------------
| Sendmail System Path
|--------------------------------------------------------------------------
|
| When using the "sendmail" driver to send e-mails, we will need to know
| the path to where Sendmail lives on this server. A default path has
| been provided here, which will work well on most of your systems.
|
*/

'sendmail' => '/usr/sbin/sendmail -bs',

/*
|--------------------------------------------------------------------------
| Mail "Pretend"
|--------------------------------------------------------------------------
|
| When this option is enabled, e-mail will not actually be sent over the
| web and will instead be written to your application's logs files so
| you may inspect the message. This is great for local development.
|
*/

'pretend' => false,

];

PHP mail() is working fine but not able to get my laravel 5.0 mail() is not working. Any suggestions. Thanks in Advance.

via Chebli Mohamed