winmail.dat Opener

How to open winmail.dat

1. Save the winmail.dat attachment from the email to your device.
2. Drop it onto the box above, or click to choose it.
3. The files that were packed inside are listed with their real names. Download one, or all of them as a .zip.

If you saved the whole email as an .eml file instead, drop that. The winmail.dat attachment will have an Open button.

Why you received winmail.dat

The sender uses Outlook or Exchange, and their message went out in Outlook’s “rich text” format. Outlook wraps the formatting and the attachments of such a message into a single container called TNEF, and attaches it under the name winmail.dat (some mail systems rename it to ATT00001.dat). Outlook on the other end unpacks it silently. Gmail, Apple Mail, Thunderbird and most phones do not, so you see one useless-looking file where the PDF or spreadsheet should be.

Nothing is wrong with your computer, and the attachment is not lost. The lasting fix is on the sender’s side: sending as HTML or plain text instead of rich text. Until they do, this page gets the files out.

What it reads

• Every attached file, with its long file name, including names with accented characters.
• The message details when they are present: subject, sender, date and the body. A body stored as compressed rich text is decompressed; if it wraps HTML, the HTML is shown, otherwise the text is shown and the original .rtf can be downloaded.
• Embedded Office objects, saved as complete files, and messages embedded inside the container, which open in place.
• Files with a bad checksum or stray data at the end still open; what can be read is shown.

A winmail.dat often holds only attachments, or only formatting. If the list is empty, the sender’s message had no real attachment and the plain-text version you already received is the whole message.

Privacy

The file is decoded by your browser. It is not uploaded, so it is safe to use for invoices, contracts and anything else people tend to send from Outlook.

Frequently asked questions

What is a winmail.dat file?

It is a container that Outlook and Exchange attach when a message is sent in Outlook’s rich-text format. It holds the message formatting and the real attachments in a Microsoft format called TNEF.

How do I get my attachment out of winmail.dat?

Save winmail.dat from the email, drop it on this page and download the files listed. They keep their original names.

Why does Gmail or Apple Mail show winmail.dat instead of the attachment?

Only Outlook understands the TNEF container. Other mail programs show it as a single unknown attachment. The sender can avoid it by sending mail as HTML or plain text instead of rich text.

I opened winmail.dat and there are no files in it. Why?

The container then holds only formatting information for a rich-text message with no attachments. The text you already saw in the email is the complete message.

Is winmail.dat dangerous?

The container itself is just packaging. The files inside are ordinary attachments and deserve the same care as any attachment from that sender. This page only unpacks them on your device; it does not run them and does not upload anything.