I have configured the email delivery with mirror page and unsub link.
When i click the mirror page link, It says not found HTTP 404.
What could be the reason behind this?
when i test the redirection sever
it returns status as OK.
Is this in a training environment or in you partner sandbox or in a customer environment?
The Mirror page is managed according to properties on the Delivery. Open the Delivery and go to Properties > Validity. The mirror pages are not kept indefinitely.
Once deliveries have gone out you should be able to go to the Delivery tab and examine the mirror pages from there.
Also, verify that the mirror page URL is set in the Deployment wizard. under the Tools menu. Click Next until you got to the Access from the Internet screen.