Q: We are using Office 365. One of our users can’t send email to one of his clients with NDR 550 5.7.350. What could be the problem?
chicagotech.net: There are many causes for the NDR 550 5.7.350.
- If this is only user in your organization has this problem, it is possible recipient block the user.
- If the user can send email without attachment, it could the attachment issue.
- If emails sent this client from everyone in your organization are rejected, it’s likely that only the recipient’s email admin can fix this problem. You may contact the recipient’s email admin and ask them to add your domain name, or the sender’s email address, to their list.of allowed senders
