<p><strong><span style="font-size: 12pt;">Problem</span></strong><br /><br />Emails sent with or without attachments are showing up with a "winmail.dat" file as an attachment.<br /><br /><strong><span style="font-size: 12pt;">Explanation</span></strong><br /><br />If Outlook sends a message using the RTF format for bold text and other text enhancements, it includes the formatting commands in the winmail.dat file. Receiving email clients that do not understand the file display it as a stale attachment. To make matters worse, Outlook may also pack other, regular file attachments in the winmail.dat file. <br /><br />For further information:<br />Associated Microsoft link <a href="http://support.microsoft.com/kb/278061">http://support.microsoft.com/kb/278061</a><br /><br /><strong><span style="font-size: 12pt;">Solution</span></strong><br /><br />Prevent Winmail.dat Attachments from Being Sent in Outlook<br /><br />Fortunately, you can get rid of winmail.dat altogether by making sure Outlook does not even try to send mail using RTF. <br /><br />To prevent Outlook from attaching winmail.dat when you send an email: <br />Select <strong>Tools</strong> | <strong>Options</strong>... from the menu. <br />Go to the <strong>Mail Format</strong> tab. <br />Under <strong>Compose</strong> in this message format:, make sure either <strong>HTML</strong> or <strong>Plain Text</strong> is selected. <br />Click <strong>Internet Format</strong>. <br />Make sure either <strong>Convert to Plain Text format</strong> or <strong>Convert to HTML format</strong> is selected under <strong>When sending Outlook Rich Text messages to Internet recipients, use this format: <br /></strong>Click <strong>OK. <br /></strong>Click <strong>OK </strong>again. <br /><br />Extract Files from Winmail.dat without Outlook:<br />If you receive winmail.dat attachments with embedded files, you can extract them using a winmail.dat decoder on Windows or Mac OS X.</p>