Troubleshooter: Suppressing Automatically Generated Message Attachments

We just merged with a company that uses Lotus Notes. We set up an SMTP connector to funnel traffic to that organization, but some messages are arriving on the Notes side with a winmail.dat file attached. How do we suppress generation of these files?

Exchange generates winmail.dat files when it thinks it's sending to a downlevel client (and for Exchange to consider Notes downlevel is understandable). However, you can force the SMTP virtual server that owns the connector not to send Rich Text Format (RTF) content (e.g., in the form of a winmail.dat attachment) to the remote side. To do so, open a registry editor and navigate to the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeTransport\Parameters registry subkey (if the Parameters subkey doesn't exist, you'll need to create it). Add a new registry entry named NonSMTPDomainEncoding of type REG_DWORD, set the value to 1, then restart the SMTP service. For a description of this registry entry and when to use it, see the Microsoft article "XIMS: SMTP Connector Ignores Setting to 'Never' Use Exchange Rich Text Format When the Recipient Address Is Encapsulated" (

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