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Thursday, June 28, 2012, 15:17

Why am I getting winmail.dat errors in my mail client?

Category: Configuration

Solution ID: 00000130


You are receiving errors from your mail client saying "can not read winmail.dat" or some similar error. You are *not* using a Microsoft e-mail client.


winmail.dat is a proprietary Microsoft method of encrypting mail. This file is generally only understood by Microsoft programs. Non-Microsoft mail clients often can not read the winmail.dat attachment. This is a very common problem.

This situation occurs when an Outlook mail client is configured to send mail using the rich text format rather than HTML. The sending mail client (Outlook) needs to be configured to use HTML markup.

NOTE: This is a change that needs to be made on the sender, so it will likely be a person outside of the local organization.

In general you can disable this behavior in Outlook as follows:

  1. Select Tools | Options... from the menu
  2. Go to the Mail Format tab. Under "Compose in this message format:", make sure either HTML or Plain Text is selected.
  3. Click Internet Format.
  4. Make sure either "Convert to Plain Text" format or "Convert to HTML" format is selected under "When sending Outlook Rich Text messages to Internet recipients, use this format:"
  5. Click OK.
  6. Click OK again.

Tags: winmail.dat, microsoft, outlook, exchange, errors, can not read

See Also:

Link to this article: kb/winmail_dat_errors

Updated: Thursday, June 28, 2012, 15:17

-- David Rutherford


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Last modified: 2012-08-27, 16:52

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