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mediumExchangeExchange Onlineupdatelearn_exchange · Jun 25, 2025
Fix NDR error 5.7.133 in Exchange Online - Exchange
Exchange Online now provides guidance on resolving NDR error 5.7.133, which occurs when messages are rejected from external or unauthenticated senders. This update helps administrators address email delivery issues and maintain proper messaging security.
“Learn how to fix email issues for error code 5.7.133 in Exchange Online (the group recipient is configured to reject messages from external or unauthenticated senders).”
View original article →Security
threat_protection
Audience
adminsecurity_engineer
Environment
cloud
Ontology Topics
AZ-500
Classification confidence: 95%
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