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I’ll pass on something I learned that may save others a lot of diagnostic time. After months of wrestling with Outlook crashes, I finally gave up on it and switched to Thunderbird. I then noticed problems with incoming messages that were created in Outlook by others. Embedded graphics and file attachments were missing and long hyperlinks were corrupted. This was a problem when opening Outlook messages in Thunderbird and some webmail apps (Yahoo Mail and others), but other webmail apps had no problem (e.g., Hotmail/Outlook.com and Verizon’s webmail app). I had not previously noticed the problem with webmail because I use POP3 to download email from webmail accounts. Long story short, this is what I learned.
When rich text is selected in Outlook as the email format, all of the rich text plus any embedded pictures/graphics and any file attachments are encapsulated in a TNEF file named winmail.dat and attached to the message. This happens only with rich text format. Outlook also leaves a plain text version of the message text in the message. In the message source, all content is word-wrapped at 76 character lines, with embedded carriage returns accomplishing the wrapping.
Outlook and some other email apps use the winmail.dat file, others don’t handle it. So, the message can appear corrupted at the receiving end if a non-compliant email client is used, get forwarded and subsequently re-opened in Outlook or a compliant email app, and appear correctly.
In a non-compliant email app, only the plain text portion of the message contents is shown. In some cases, it may show that there is an attachment named winmail.dat. If the message contains a long hyperlink, the non-compliant email app recognizes only the first wrapped line (76 characters) as a link. Subsequent lines of the URL are plain text. Highlighting all of the hyperlink text and pasting it in the browser’s URL box will work in some cases and not others depending on whether the embedded carriage returns are ignored or included.
Use of the winmail.dat file does not involve anything proprietary to Microsoft; it is just something different they chose to do to minimize potential corruption to rich text emails. Some publishers of email apps have provided for handling it, others have not.
Solutions:
When rich text is selected in Outlook as the email format, all of the rich text plus any embedded pictures/graphics and any file attachments are encapsulated in a TNEF file named winmail.dat and attached to the message. This happens only with rich text format. Outlook also leaves a plain text version of the message text in the message. In the message source, all content is word-wrapped at 76 character lines, with embedded carriage returns accomplishing the wrapping.
Outlook and some other email apps use the winmail.dat file, others don’t handle it. So, the message can appear corrupted at the receiving end if a non-compliant email client is used, get forwarded and subsequently re-opened in Outlook or a compliant email app, and appear correctly.
In a non-compliant email app, only the plain text portion of the message contents is shown. In some cases, it may show that there is an attachment named winmail.dat. If the message contains a long hyperlink, the non-compliant email app recognizes only the first wrapped line (76 characters) as a link. Subsequent lines of the URL are plain text. Highlighting all of the hyperlink text and pasting it in the browser’s URL box will work in some cases and not others depending on whether the embedded carriage returns are ignored or included.
Use of the winmail.dat file does not involve anything proprietary to Microsoft; it is just something different they chose to do to minimize potential corruption to rich text emails. Some publishers of email apps have provided for handling it, others have not.
Solutions:
- There used to be a Thunderbird add-on (LookOut), that handled the winmail.dat file. It has not been maintained and is not compatible with the current version.
- Ask the message sender to change their Outlook setting to HTML and recreate and resend the message.
- Use an email client that handles the winmail.dat file.
- Forward the message to an email client that handles the winmail.dat file.
- Complain to the publishers of non-compliant email apps to make them aware of the issue and request a fix. So far, I have heard from Yahoo. They choose not to deal with the problem but did apologize for any inconvenience.
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