If you regularly receive emails from Windows users who use Microsoft Outlook as their email client, you may have received attachments with the name “winmail.dat”. couldn’t open it. In this article, we’ll take a deep dive into winmail.dat files, explaining what they are and how you can open them on your Mac. we’ll also tell you why you might not want to open them.
what is a winmail.dat file?
The .dat extension simply means that the file is a data file. that data can be just about anything, including text, graphics, or even video. because macos doesn’t know what kind of data the file contains, it can’t assign an app to open it. you can open it in a text editor and try to determine what kind of data is in the file, then manually choose which application to try and open in it by right clicking the file in finder and selecting ‘open with’ from the context menu.
For this article, however, we are dealing with a specific type of .dat file, one called winmail.dat. A winmail.dat file is one that Microsoft Outlook creates as a data container. In some cases, the sender of the email has configured Outlook to compose messages in Rich Text Format (RTF). and while the mac can happily read and write rtf files, somewhere between the message being encoded by outlook or microsoft exchange and being sent, the message is attached with a winmail.dat file. In some cases, the winmail.dat attachment may be an actual attachment, such as a word document or calendar invitation that has been incorrectly encoded.
how to open a winmail.dat file on your mac
The first thing to say about opening winmail.dat files is: be careful. As a general rule, you should never open any email attachment unless you are sure what it is and you trust the sender of the email. The fact that an attachment arrives in your inbox with the generic name “winmail.dat” means that you can’t tell what it is or if the recipient intended to send it.
The second thing to say is that, as we explained earlier, it could be that the attachment is nothing more than a rich text version of the text in the body of the email.
so before you try to open the attachment, ask the sender what they intended to send you and if your email should have had an attachment. if the answer is no, the attachment is likely the rich text version of the email. To prevent this from happening in the future, you can ask the sender to configure Outlook to compose emails as plain text or HTML. that should prevent the winmail.dat file from being attached.
how to open a winmail.dat file on your mac in a browser
if you’re sure you want to open the .dat file on your mac without contacting the sender, do the following:
- save it to your desktop using your email client’s save attachments feature; In apple mail, you can right click on the attachment and select save.
- In a web browser, go to winmaildat.com
- click choose file and navigate to the attachment you saved.
- press upload.
- click start.
How to open a winmail.dat file in Gmail
Google’s web-based gmail client is adept at identifying whether winmail.dat files are just rich text versions of an email message or what type of document the attachment should be. So if you have a gmail account, forward the email, and then navigate to gmail.com in a web browser, sign in, and open the forwarded message there.
how to open a winmail.dat file by saving it in the correct format
If the sender tells you they intended to send an attachment, ask what type of file they sent. you can then save the attachment with a meaningful name and a file extension that can be opened by an application that opens that type of file. for example, if it was a word document, save it as a .doc or .docx. if it was a calendar invite, save it as .ics.
how to open a winmail.dat file using enough of tnef
TNEF’s Enough is a macOS app designed to identify open winmail.dat files. Download it from the Mac App Store, launch it, drag the winmail.dat attachment onto it, or right-click the attachment and choose ‘Open with’ and TNEF’s Enough. Once the application has opened it, you can export it in the correct file format.
As you can see, there are several ways to open winmail.dat files on your Mac. however, before doing so, you should make sure you know who sent it and what is in it. our favorite method is the gmail method because it’s so simple. but any of the others should work too.