What is the Winmail.dat file?

The Winmail.dat file holds information for the Microsoft Outlook Rich Text format when Word is used as the e-mail editor. When you send a message to someone whose client doesn’t support Rich Text format they will receive the message with the Winmail.dat file as attachment.

When a receiver whose client doesn’t support Rich Text format gets a message that has a Winmail.dat attachment it could be the case that any other attachment that got sent with the message will be in the Winmail.dat file and therefore inaccessible for the receiver.

To prevent this behavior make sure you don’t send Rich Text formatted messages to people who do not support it. Microsoft Office Outlook and Outlook Express both support Rich Text formatted messages.

From best to least compatible with other mailclients;

• Plain Text
• HTML
• Rich Text

Solution 1

When you mainly send to people who are using Microsoft Office Outlook and want to continue using Rich Text formatted messages it is best you change the format on a per message basis for the people who are not compatible with Rich Text format.

1. Create a new message
2. Choose Format-> Plain Text
3. Once you have chosen for Plain Text you can use the Format menu again to change back to Rich Text or HTML

Solution 2

If you want to get rid of the Rich Text format default you can change this in Tools-> Options-> tab Mail Format. You can change to Rich Text just for one message.

When you are using Plain Text as default

1. Create a new message
2. Choose Format-> Rich Text

When you are using HTML as default

1. Create a new message
2. Choose Format-> Plain Text
3. Choose Format-> Rich Text

Solution 3

You can also change the default message format on a per user or even a per e-mail address basis.

1. Open the contact from the Contacts folder
2. Double-click on the e-mail address of the contact
3. In the Internet Format dropdown list choose the format you want to use for this specific contact’s e-mail address