winmail.dat with Mail Opener
This opens a sample winmail.dat sent by John Doe. Inside are a floor plan PDF and notes with an accented name, plus the formatted message. Open the winmail.dat or ATT00001.dat you received and the real attachments are listed, ready to save.
- Save the winmail.dat or ATT00001.dat attachment from your mail app.
- Tap Open your email file and choose it; the name does not matter, the content is recognised.
- The files packed inside are listed with their real names.
- Save or share each file. The message itself is shown below the list.
What to know
winmail.dat is Outlook's Transport Neutral Encapsulation Format (TNEF). When Outlook sends in its rich-text format to an address it does not know, it packs the formatting and the attachments into one file, application/ms-tnef, and the receiving mail app shows only that file, often renamed ATT00001.dat. Nothing is lost: the files are inside.
Mail Opener reads the TNEF stream in the browser: each attachment, its long file name from the MAPI properties (Unicode names included), its type, and an embedded message if one was attached. The body is usually compressed RTF; when the RTF carries HTML it is shown formatted. The tool's test suite compares the extracted files byte for byte with the Debian tnef command.
Updated · Cosmovex
Questions
Why do I get winmail.dat instead of the attachment?
The sender's Outlook used rich-text format for your address. The sender can avoid it by sending in HTML or plain-text format; until then, open the winmail.dat here to get the files.
Is ATT00001.dat the same thing?
Often yes. Some mail apps rename winmail.dat to ATT00001.dat. Mail Opener reads the content, so the name does not matter. If an ATT00001.dat is not TNEF (some are just a part of the email body), the page says it is not an email file.
The winmail.dat has no attachments listed. Why?
Some winmail.dat files carry only the formatted body and no files. The body is still shown.
Is my email uploaded anywhere?
No. The file is read by the page in your browser. The only request to us is a count for the free daily limit, which carries a random ID for this browser and the kind of file, never the email, its subject, its sender or its attachments.
The free plan covers everything on this page. Mail Opener Pro ($9.50 until Oct 25, then $19, paid once) is described on the Mail Opener page.
