I getting following error while sending mail to local user of my mail server.

<user2@mydomain.com>: host 127.0.0.1[127.0.0.1] said: 503 5.5.1 id=00827-01-5 - Rejected by MTA on relaying, from MTA([127.0.0.1]:10025):
503 5.5.1 Error: nested MAIL command (in reply to end of DATA command)



In details:
From: Mail Delivery System [mailto:MAILER-DAEMON@mail.mydomain.com]
Sent: 16 December 2013 10:43
To: user1@mydomain.com
Subject: Undelivered Mail Returned to Sender
This is the mail system at host mail.mydomain.com.

I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can delete your own
text from the attached returned message.
The mail system
<user2@mydomain.com>: host 127.0.0.1[127.0.0.1] said: 503 5.5.1 id=00827-01-5 - Rejected by MTA on relaying, from MTA([127.0.0.1]:10025):
503 5.5.1 Error: nested MAIL command (in reply to end of DATA command)