When an external mail is sent out from outlook 2010 configure to exchange server, the mail is not delivered and bounces back with the message below:

Delivery is delayed to these recipients or groups: 

check your mail queues, make sure your send connectors are setup right, and if you coudl provide the full ndr that would be helpful as well. 

As suggested providing full NDR will help to identify the issue.

Try to telnet hotmail.com from your n\w and drop an email through telnet and see if its successful

enable protocol logging on the send and receive connectors

Check your messaging tracking logs

check for the last error on the queue

Hi otobs,

Thank you for your question.

Did you try to send email by OWA to check if it bounce back?

Did all external email bounce back?

We could check  SMTP queues (get-queue) and then the messages within the queues (get-Queue | Get-message). If you have a message sitting in your queue that is waiting to be delivered, then the next hop outside of your Exchange server (DNS/smarthost/firewall/etc) is not accepting the message for delivery.

Some issues may include:

1. Delays in your Exchange-aware antivirus scanning preventing outbound delivery

2. File-level antivirus exclusions not properly set on Exchange server

3. Invalid DNS server settings on your Exchange server

4. Exchange server performance (check event logs)

5. Poor network communication between Exchange and next hop

If there are any questions regarding this issue, please be free to let me know.

Best Regard,