There may be a number of reasons why you’re unable to send or receive emails in Outlook for Exchange. Try the following steps:

1. Check to see if you’re connected to the internet.
   
2. Verify if your Outlook settings have been configured correctly.
   
3. Make sure your Outlook version is up to date.
   
4. Check if you have any anti-virus or firewall software blocking access to the mail server.
   
5. See if you can access emails through the web-based mailbox interface.
   
6. Verify if your mailbox is over its size limit.