Cpanel Can't Send Mail To External Mail

I have migrated my cpanel server from one to other server. After finishing migration. All email account can't send mail to external mail such as to "yahoo mail".

Here, some log:
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Return-path: <test@mydomain.com>
Received: from localhost ([127.0.0.1] helo=mydomain.com)
by server.hostname.com with esmtpa (Exim 4.69)
(envelope-from <test@myadomain.com>)
id 1N1wop-0004bE-ST
for someone@yahoo.co.uk; Sun, 25 Oct 2009 09:43:11 +0300
Received: from XXX.161.156.165 ([125.161.156.165])
(SquirrelMail authenticated user test@myadomain.com)
by mydomain.com with HTTP;
Sun, 25 Oct 2009 09:43:11 +0300 (MSK)
Message-ID: <14566.XXX.161.156.165.1256452991.squirrel@domain>
Date: Sun, 25 Oct 2009 09:43:11 +0300 (MSK)
Subject: Test mail
From: test@myadomain.com
To: someone@yahoo.co.uk
User-Agent: SquirrelMail/1.4.13
MIME-Version: 1.0
Content-Type: text/plain;charset=iso-8859-1
Content-Transfer-Encoding: 8bit
X-Priority: 3 (Normal)
Importance: Normal

just test

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Domain and mail account are edited.