Dealing With Winmail.dat Problems

The Problem

Email users sometimes find that they receive email messages with a strange file attached, called winmail.dat. When they attempt to open this file, either it can’t be opened at all, or it contains “garbage” data.

The situation is a direct result of Microsoft Outlook’s bad behavior with attachments. Microsoft’s assumption that all people should and would use Outlook for an email client has caused many problems with people send each other files with different email clients. Shouldn’t people be allowed to have a choice of email client? Yes!

To make matters even more frustrating, this causes problems, not for the sender of the email, but the recipient, particularly when actual files are attached to messages. Outlook email senders often times do not know that their attachments are being “messed up” upon reaching the recipient.

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
• formatted with the HTML formatting language so that it appears (sort of) like a web page
• formatted as a Microsoft Word document.

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. This winmail.dat file contains formatting information, in a human-unreadable form, 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!

The Send Solution

Microsoft has instructions at this knowledge base article. Go to this website: http://support.microsoft.com/kb/278061. To paraphrase the information, there are 2 processes that need to be followed by the email sender who uses Outlook.

1) 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.

2) Use the following steps to remove the RT 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 the clear the always send to this recipient in Microsoft Exchange rich text format check box, and then click OK.

The Recipient Solution

There are many tools available for opening winmail.dat files in Windows, Macs and Linux variations. Some Windows solutions include Winmail Opener, Fentun and TNEFView. On the Macintosh, TNEF’s Enough works well. Mac users can also use OMiC, an Apple Mail plugin that decodes winmail.dat inside that email client. TNEF can be compiled for Linux variants as well. ktnef is part of KDE now, as well as Fentun for Linux.

Ultimately, training MS Outlook users and being helpful to them will provide the best long term results. Don’t send nasty emails back to winmail.dat offenses against you. Remember, Microsoft can make user computers do bad things; its not the user’s fault.