Since 01/05/2015 all emails sent were returned undelivered. This is the first time such problem is happening to me after five years of using Office Outlook web Access (Microsoft Exchange). Any great ideas to take me out of this dilemma. Thank you.

What's the message in the returned email?

Do you see any messages stuck in the queue in exchange? If so, they should give you a detailed reason as to why they're not being sent.

Hi Siyabu,

According to your description, I know that you cannot send email and get NDR.

How is the impact, one user or all users, Outlook only or both of Outlook and OWA? How about receiving message?

Please verify whether this issue caused by Firewall.

Please try to re-configure the Send Connector.

Detailed information about NDR without sensitive information would be helpful for the further troubleshooting.

 

Thanks