A user tries to send an email to firstname.lastname@example.org and receives an NDR. I sent a test mail using user's mailbox and the external user confirms that he received that email. I've checked at my server end and we are not using TLS settings.
Below is the NDR:
From: System Administrator
Sent: Monday, February 09, 2009 8:39 AM
Subject: Undeliverable: heavy rain
Your message did not reach some or all of the intended recipients.
Subject: heavy rain
Sent: 2/9/2009 8:39 AM
The following recipient(s) could not be reached:
email@example.com on 2/9/2009 8:39 AM
The recipient could not be processed because it would violate the security policy in force
<Mailbox_server_name.test.com> #5.7.0 smtp;530 5.7.0 Must issue a STARTTLS command first>
Environment: Exchange 2003+SP2.
Any help is highly appreciable.