Mac tip: Why do Outlook mail messages arrive as "winmail.dat" attachments?Laurie writes: I have a Mac, iPhone and iPad and I use Apple Mail. When my husband sends or forwards an email to me from Outlook using his PC, the attachments arrive as “winmail.dat” and I can’t open them.

Every search I have made on this subject says that this is just a problem between Outlook and Mail. Many forums recommend 3rd party software to open the attachments. You have got to be kidding! We shouldn’t have to be bouncing around with multiple programs just to do something as simple as see an attachment.

Is there a setting I am missing?

Hi Laurie! Nope, you’re not missing anything—and yes, there are occassions when Outlook and the Mac’s Mail app don’t play well together.

Specifically, Outlook has its own, unique method for formatting email messages that many other email clients can’t quite decode.

When that happens, the body of the message turns into an attachment named “winmail.dat”—and no, your Mac can’t open it without help from a third-party program. Annoying, but true.

Outlook Rich Text settings

Too many mail messages arriving as “winmail.dat” attachments? Windows users can set Outlook to disable the culprit: “Rich Text” formatting.

The good news is that your husband can set Outlook to deactivate its so-called “Rich Text Format” (which lets Outlook users compose messages with fancy fonts and other features) when sending messages to non-Outlookers.

Here’s how…

Note: The steps below are for Outlook 2013; the instructions may (and probably will) differ for earlier versions of Outlook.

  • Open Outlook, click the File menu, then select Options.
  • Click the Mail tab on the left side of the Outlook Options window, find the “Compose messages” section, then change the setting for “Compose messages in this format” from “Rich Text” to “HTML” or “Plain Text.”
  • Does your husband want to keep his “Rich Text” setting? If so, he can scroll down to the “Message format” heading, find the “When sending messages in Rich Text format to Internet recipients” setting, then select “Convert to HTML format.”

OK, but what about mail messages you’ve already received with cryptic “winmail.dat” attachments?

Well, there are (as you mentioned) several apps in the Mac App Store that’ll open winmail.dat attachments for you, but they all cost a few bucks.

A highly recommended free option, though, is a program called “TNEF’s Enough.” Just download, install and launch the app, then drag a winmail.dat file onto TNEF’s Enough dock icon to open the attachment.

Looking for more Mac tips? Click here!

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