مشکل ارسال ایمیل و deliver نشدن اون

سلام
من یک vps لینوکسی دارم که روی اون centos 6 دارم
و با whm هاستینگ را اندازی کردم
متاسفانه نمیتونم ایمیل ارسال کنم
البته ارسال میشه اما deliver نمیشه و مثلا وقتی برای gmail ایمیل میفرستم این پیغام رو بر میگردونه

کد:

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To: admin admin <[mygmail]gmail.com>
Subject: WHMCS Cron Job Activity
Date: Wed, 26 Feb 2014 05:00:01 +0000
From: WHMCompleteSolution <noreply@yourdomain.com>
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Cron Job Report for 26-02-2014 05:00:01

Updated Currency Exchange Rates

0 Invoices Created

0 Overdue Invoice Reminders Sent

0 Invoice Payment Reminders Sent

0 Upcoming Domain Renewal Notices Sent

0 Cancellation Requests Automatically Processed

0 Services Suspended

0 Fixed Term Services Terminated

Email Marketer Processing

Disk & Bandwidth Usage Statistics Updated



http://www.yourdomain.com/whmcs/admin/



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<font style="font-family:Verdana;font-size:11px"><p>Cron Job Report for 26-02-2014 05:00:01<br><br>Updated Currency Exchange Rates<br><br>0 Invoices Created<br><br>0 Overdue Invoice Reminders Sent<br><br>0 Invoice Payment Reminders Sent<br><br>0 Upcoming Domain Renewal Notices Sent<br><br>0 Cancellation Requests Automatically Processed<br><br>0 Services Suspended<br><br>0 Fixed Term Services Terminated<br><br>Email Marketer Processing<br><br>Disk & Bandwidth Usage Statistics Updated<br><br></p><p><a href="http://www.yourdomain.com/whmcs/admin/">http://www.yourdomain.com/whmcs/admin/</a></p>



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از طریق خود webmail هم همین مشکل وجود داره
به نظر شما مشکل از کجاست؟

کدام دیتا سنتر سرویس دارید؟

از Redstation به cpanel تیکت زدم میگه مشکل از dns !
mx رو چطوری باید تنظیم کنم؟ یعنی چه تنظیماتی باید داشته باشه؟