The sender is receiving a bounce back with the error "550 5.7.1 Message rejected as spam by Content Filtering"
Error: "550 5.7.1 Message rejected as spam by Content Filtering"
Exchange server have built in filtering features that can block certain emails if they match their content filtering rules. Email messages that are empty in content ( or nearly empty) may be caught by one of the default filtering options turned on in Exchange 2007/2010. This error is generated by the default-enabled Content Filtering anti-spam option under Hub Transport>Anti-Spam.
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