Winmail.dat attachment appears on some email messages. In some instances this issue can mean that any message or attachment are not shown and instead all you see is the winmail.dat attachment.
Changing the options of the mail client can eliminate the delivery of the winmail.dat attachment. If the email is a meeting request the sender should make sure that under their Calendar options in Microsoft Outlook that they have enabled the setting "When sending meeting requests outside of your organization, use the iCalendar format" (for Outlook 2010).
Please review the Microsoft document below:
|Product:||MailEnable (Custom: Custom: Custom: Custom: Custom: Custom: Custom: All Versions)|
|Keywords:||winmail.dat attachment winmail dat .dat attachments messages message|
|Class:||INF: Product Information|
|Revised:||Wednesday, May 4, 2016|