I have a user that is trying to send an email to a user in the company but the emails keeps bouncing with the error:
This message was rejected by the recipient email system. Please check the recipient's email address and try resending this message, or contact the recipient directly. For more tips to resolve this issue see DSN code 5.1.0 in Exchange Online. If the problem continues contact your help desk.
When I carryout message tracking I get the following:
SMTP: Message submitted to Advanced Queuing
SMTP: Started Message Submission to Advanced Queuing
SMTP: Message Submitted to Categorizer
SMTP: Message Categorized and Queued for Routing
SMTP: Non-Delivery Report (NDR) Generated
I can however receive the message if it is sent to the administrator email address.
They have a SBS 2003 setup with Exchange 2003.
They use Sophos Pure message for Anti-spam but have gone through this and cannot see anywhere that this email address could be blocked. I have added it to the safe senders list too.
There are no rules in outlook that could be blocking the either.
Is there anything else that I could check?