XADM: Winmail.dat Attached to All Internet Messages Regardless of Setting on Client

A file named Winmail.dat may be attached to all outgoing Internet e-mail messages, regardless of the message format that you choose in the client software.

This issue can occur if, in the Exchange System Manager snap-in, Internet Message Formats is set to force all of the messages to use Rich Text Format.

Recipients who do not use Microsoft Outlook or a Rich Text Format-aware client application cannot display Rich Text Format, and so the Winmail.dat file, which contains the Rich Text Format information, is attached to the e-mail message.

To resolve this issue, change the Rich Text Format setting:

1. Open the Exchange System Manager snap-in.
2. Click to expand Global Setting.
3. Click Internet Message Formats.
4. In the right pane, click to select the appropriate SMTP domain, and then double-click it to open its properties.
5. Click the Advanced tab, and then under Exchange rich-text format, click one of the following, as applicable (do not click Always Use):
   • Never Use. All of the mail that is addressed to this domain is sent in plain text format.
   • Determine by individual user settings. The format that the mail addressed to this domain is sent in depends on the settings of the client software.

For additional information about Rich Text Format and Microsoft Transport-Neutral Encapsulation Format (TNEF), click the article number below to view the article in the Microsoft Knowledge Base: