your message couldn't be delivered

Contributor

Hi experts 

A user from external domain(user@extdomain.com) has sent an email to one of my office365 user(myuser@contoso.com).

user@extdomain.com got the below NDR. Experts help me in troubleshooting this issue.

Your message to myuser@contoso.com couldn't be delivered
Security or policy settings at contoso.com have rejected your message

rej.JPG

1 Reply
Looks like you’ve blocked the external domain! Check the exchange online settings!