Open winmail.dat and Extract the Attachments

How to open a winmail.dat file

1. Save the winmail.dat attachment from the email to your computer. Some mail apps call it ATT00001.dat or untitled.dat; the name does not matter.
2. Drop the file onto the box above, or click Choose file.
3. Click Extract attachments. The tool reads the file and lists every attachment with its original name and size.
4. Download the files one by one, or click Download all as ZIP. The message text, if the sender's Outlook stored it, is offered as an HTML, RTF or text file.

Why emails arrive with winmail.dat

Outlook can send messages in its own Rich Text Format. To carry that formatting, together with things like voting buttons and meeting requests, it packs the message text and every attachment into one file in Microsoft's Transport Neutral Encapsulation Format (TNEF). Outlook on the other side unpacks it invisibly. Mail programs that do not understand TNEF show the package as a winmail.dat attachment instead, and the real attachments seem to be missing.

Nothing is wrong with the file, and it is not a virus by itself. It is a container, and this tool opens it in the same way Outlook would. See our guide to .dat files if your .dat file did not come from an email.

How the sender can stop it

The fix is on the sender's side. In Outlook for Windows, the sender should go to File > Options > Mail, set Compose messages in this format to HTML, and under Message format set When sending messages in Rich Text format to Internet recipients to Convert to HTML format. If the problem affects only one recipient, Outlook may have that contact saved with rich text formatting; removing the contact from the autocomplete list and typing the address again resets it.

In organisations that use Exchange Online or Exchange Server, an administrator can stop TNEF for outside domains with the PowerShell command below.

Set-RemoteDomain -Identity Default -TNEFEnabled $false

Supported files and limitations

• Accepts winmail.dat files. The format is checked from the file's contents, not only its extension.
• One file at a time, up to 100 MB, and at most 200 output files.
• Files are processed one at a time in a background thread, so the page stays responsive.

One winmail.dat file at a time, up to 100 MB, with at most 200 attachments.

Attachments are extracted exactly as the sender attached them. Programs and scripts among them are marked; open them only if you were expecting them.

Calendar invitations and contact cards stored as Outlook properties rather than as attached files are not converted to .ics or .vcf.

If the message text was sent as compressed RTF, it is saved as an .rtf file that Microsoft Word or LibreOffice Writer opens.

Privacy and security

Your files are opened and processed by your own browser. The ExeDepot server only delivers this page and its scripts; it never receives your files, their contents or their names. The page loads no third-party scripts or ads, and its Content Security Policy allows connections only back to exedepot.com.

Results exist only in your browser's memory until you download them, and they are discarded when you click Start over or close the tab. No online tool can promise perfect security, so keep your browser up to date, and for documents you would never put online consider an offline desktop app such as Thunderbird.

Frequently asked questions

What is winmail.dat?

It is a package created by Microsoft Outlook when it sends a message in Rich Text Format. It holds the formatted message text and the attachments. Mail programs other than Outlook often cannot unpack it and show it as a winmail.dat attachment.

Is winmail.dat safe to open?

The file itself only holds data. The attachments inside it carry the same risk as any email attachment, so check unexpected programs, scripts and Office files with macros before you open them.

How do I open winmail.dat on my phone?

Open this page in your phone's browser, tap Choose file and select the winmail.dat you saved from the email. The extraction runs on the phone itself.

Are my emails uploaded?

No. The winmail.dat file is read and unpacked in your browser. Neither the attachments nor the message text are sent anywhere.

Why does Thunderbird show winmail.dat?

Thunderbird does not unpack TNEF by itself, so it shows the package as an attachment unless an add-on handles it. Saving it and opening it here works with any mail program.