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Why do some of my incoming emails contain a winmail.dat file?

Email users sometimes find that they receive email messages with a strange file attached: winmail.dat. When they attempt to open this file, either it can't be opened at all, or it contains "garbage" data. In this article we explain the problem and offer solutions to help correct it.

The Problem

The reason email users sometimes see the winmail.dat file attached to incoming email is because they are using several different email client programs to receive, read, and send email. The most commonly used email client programs at GPC seem to be Microsoft Outlook and Netscape (specifically the Messenger component), with a small minority using Eudora. Unfortunately, Outlook does not "play nice" with the other email programs all the time. This causes problems, not for the sender of the email, but the recipient, particularly when actual files are attached to messages.

Outlook 97/2000

Outlook is a rather powerful email client program with a number of features that look very attractive. Most notably, Outlook allows users to send email in a variety of formats:

  • as plain vanilla text with no formatting
  • in Rich Text Format, which allows for a limited amount of formatting, such as boldface/italic/underlined text or different fonts
  • in HTML formatting language so that it appears (sort of) like a web page
  • with Microsoft Word formatting

It's these formatting options that cause the problems.

When an Outlook user composes and sends a message using either Rich Text Format or HTML Format, Outlook automagically generates a file, winmail.dat, and attaches it to the end of the message. Winmail.dat contains formatting information that Outlook will use on the receiving end to display this email message correctly. Unfortunately, Outlook is the ONLY email client program that can use this information! Netscape Messenger, Eudora*, and other email client programs don't understand it.

The Solutions

If you are receiving these winmail.dat files

One solution to the problem is to visit and download the WMDecode program found there (look about halfway down the page). This will at least allow you to decode the winmail.dat files and extract any useful attachments from them.

Other than this, there's not much you can do on your end to fix the problem, since it's not your email program generating the issue. You might reply to the individual who sent you the offending email and ask that they re-send the message with the attached files as a plain text message rather than in Rich Text Format or HTML.

If you are sending these winmail.dat files

If someone emails you to complain that they couldn't read your attachments, or to ask what the "winmail.dat" file is that you sent them, chances are you sent the email using Microsoft Outlook 97/2000 (or, as a very remote possibly, another product using Microsoft Exchange Server).

There are multiple ways to fix the problem, depending on how you have set up your address book capabilities and whether or not you are using a mailing list or group mailing to send out the offending email. Please read the remainder of this section before you begin making changes to your settings as there are two special situations, discussed first, that you must consider before choosing the appropriate solution.

Special Situations

If you are sending messages to a mailing list or as a group mailing

In this situation, you MUST set ALL users up to receive plain text email. If even one user is set up in your address book to receive Rich Text Format or HTML format email (or if these formats are your default), everyone will receive that format. You must either edit every address book entry for every individual on your mailing list, or change your default sending mode to plain text. Both methods are described below.

If you use an online directory (LDAP server) to look up the recipient's address

In this situation, you have no address book entry to edit, so you may either change your default sending mode to plain text or change the sending mode manually for each message.


Solution details

If the recipient is in your address book

  1. Open up your Outlook Address Book, either by clicking on the Address Book icon or by choosing Tools and then Address Book.
  2. Select the recipient's entry in your address book and open up their Properties, either by clicking on the Properties button or double-clicking on the recipient's entry.
  3. Select the Name tab in the Properties dialog window.
  4. Check the Send email using plain text only box at the bottom of the window.
  5. Click the OK button.

If you enter the recipient's address manually in the To: line of your email message

EACH TIME you send a message to this person, you must:

  1. Create a new email message as you normally would, but before sending it,
  2. Choose Format and then Plain Text from the menu bar.
  3. Now send your message.

If you want to change your default sending mode

Change your default sending mode in Outlook, thereby sending all email messages as plain text, by doing the following:

  1. Select Tools and then Options from the Outlook menu bar.
  2. Select the Mail Format tab in the dialog window.
  3. In the first drop-down list, under Message Format, select Plain Text
  4. Click the OK button.

* Eudora can, and does, display HTML formatted email in HTML format, but it does not use the winmail.dat information to do so.

Disclaimer: Please note that this material is referenced from

Psmail does not own or copyright materials referenced/collected from remote websites like this one.

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