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Login to Microsoft 365 Defender: Policies & rules --> Threat policies --> Anti-spam policies
https://security.microsoft.com/antispam Edit the "Connection filter policy (Default)" or make a new rule to allow the IP address(s). An example error: Message Delivery Failure. Attempt (0): Could not connect to mail server for domain. The remote mail server could not be contacted at this time. Message has been requeued. Keywords: Email, E-Mail, 365, Hosted, Whitelist, Allow |