This article was previously published under Q278061
You receive an email message that contains a winmail.dat attachment. This issue may occur if all of the following conditions are true:
The email message is sent to you by someone using Microsoft Outlook.
The format of the message is Rich Text format (RTF).
This issue is more common when the email message is sent to you over the Internet.
The Winmail.dat file is used to preserve Rich Text formatting. Outlook uses it when sending a Rich Text-formatted message. During transport, the content of the message may be changed, preventing the receiving client from being able to read the formatting instructions. In other cases, the receiving client does not use or recognize the winmail.dat file.
The data in a winmail.dat file is not usable. To resolve this issue, ask the sender to re-send the message in plain text format. The following methods can be used by sender to prevent sending Rich Text messages encapsulated in the Transport Neutral Encapsulation Format (TNEF).
Method 1: Change the default message format
The sender can change the format of the email messages that they send by using the following steps:
On the Tools menu, click Options, and then click Mail Format.
In Compose in this message format, click to select Plain Text, and then click OK.
NOTE: To send to certain recipients that use RTF format and others recipients that use plain text format, the sender must set the option for the recipient in either the Personal Address Book or the recipient's contact record.
Method 2: Modify the recipient's entry in the Personal Address Book
The sender can use the following steps to remove the RTF format from the recipient attribute in the Personal Address Book:
On the Tools menu, click Address Book.
In Show Names From, click the Personal Address Book.
Select the addressee that you want to set as plain text, and then click Properties on the File menu.
In the SMTP-General tab, click to clear the Always send to this recipient in Microsoft Exchange rich text format check box, and then click OK.
Method 3: Change the specific contact format
The sender can use the following steps to set plain text in the recipient's contact record:
Open the recipient's record in the Contacts folder.
Double-click the recipient's e-mail address.
In the E-Mail Properties dialog box, click Send Plain Text only under Internet Format.
Method 4: Set the Outlook Rich Text Format Internet e-mail setting
In Outlook 2003 and Outlook 2007, click Options on the Tools menu.
Click the Mail Format tab.
Click Internet Format.
Under Outlook Rich Text options, click either Convert to HTML format or Convert to Plain Text format.
For more information about TNEF, click the following article number to view the article in the Microsoft Knowledge Base:
290809 How e-mail message formats affect Internet e-mail in Outlook
For more information about Winmail.dat attachments, click the following article numbers to view the articles in the Microsoft Knowledge Base:
149203 Preventing Winmail.dat from being sent over IMC
138053 How to prevent the Winmail.dat file from being sent to Internet users