Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have a client (who is on a Windows 7 machine - Office 2012) who keeps trying to send me an attachment (I believe its just a plain text file).

He is sending it as an attachment through Outlook, and I am also using Outlook to receive the message. I am not getting his attachment however, and the only thing attached to the email is a file called winmail.dat.

I found this article here that kind of explains what winmail.dat is, but was hoping for a little bit more technical of an explanation from any Windows gurus:

  • What is winmail.dat?
  • Why is it being created?
  • How can my client prevent this from happening?
  • If my client isn't technically-savvy enough (which he isn't) to fix this himself, what are some recommended & free tools I can use to inspect it? If I use Microsoft Word, it spits out a lot of garbage and its tough to decipher what I'm seeing.

Thanks for any help here.

share|improve this question

Have this person set his mail client to only send in Plain text or HTML but NEVER in Rich text!

When you use Microsoft Outlook to send messages through the Internet with attachments and you use the Microsoft Outlook Rich Text format, some recipients report that the message includes an additional file called the Winmail.dat file. The Winmail.dat file is usually very small, but you cannot open it in the message. The original message attachment is not always separate from the Winmail.dat file attachment, and may be included in the Winmail.dat file attachment. CAUSE

This problem occurs because the Winmail.dat file is used to preserve formatting that the sending client includes in the message, but the receiving client does not recognize the Winmail.dat file. In Outlook, the Winmail.dat file includes Rich Text Formatting (RTF) instructions. This type of formatting is used with the Microsoft Outlook Rich Text format and when you use Microsoft Word as your e-mail editor. RESOLUTION

To resolve this problem, use the plain text format. To do this:

  1. On the Tools menu, click Options, and then click Mail Format.

  2. 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, you must set the option for the recipient in either the Personal Address Book or the recipient's contact record.

Use the following steps to remove the RTF format from the recipient attribute in the Personal Address Book:

  1. On the Tools menu, click Address Book.

  2. In Show Names From, click the Personal Address Book.

  3. Select the addressee that you want to set as plain text, and then click Properties on the File menu.

  4. 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.

Use the following steps to set plain text in the recipient's contact record: 1. Open the recipient's record in the Contacts folder.

  1. Double-click the recipient's e-mail address.

  2. In the E-Mail Properties dialog box, click Send Plain Text only under Internet Format.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.