A winmail.dat arrives when someone using Outlook sends an email in Outlook's own Rich Text format to a program that is not Outlook. Outlook wraps the formatting and every attachment into one file in its TNEF format and calls it winmail.dat, sometimes ATT00001.dat. Apple Mail, the iPhone's Mail app, Thunderbird and most phone apps cannot read it, so the PDF or spreadsheet you were meant to get seems to be missing.
Nothing is lost: the files are inside the winmail.dat. This page unpacks it and lists each attachment to save, exactly as it was sent, with the message text beneath. It is free to use, with no account and no upload limit, and it runs entirely in your browser: nothing is uploaded, and it keeps working offline once it has loaded.
- Why did I get a winmail.dat instead of the attachment?
- The sender's Outlook sent the message in Rich Text format, which only Outlook understands, so it packed the attachments into winmail.dat for the trip. Your mail program received everything; it just cannot unpack that format. It happens most often when Outlook on Windows sends to Apple Mail, an iPhone or Thunderbird.
- How can the sender stop sending winmail.dat?
- In Outlook, choose File, then Options, then Mail, and set Compose messages in this format to HTML. Then, under Message format, set the option for sending to people outside the organisation to convert to HTML rather than Rich Text. An address saved with the "send using Outlook Rich Text Format" setting needs that changed too, or deleting from the autocomplete list and typing again.
- Is it safe to open the files from a winmail.dat?
- Looking is safe: this page reads the file and runs nothing in it. The attachments themselves are whatever the sender attached, saved exactly as they were, so treat them as you would any attachment: open a document or a program only if you trust whoever sent it.
- The winmail.dat has no attachments in it. Why?
- Sometimes Outlook sends one just to carry the formatting, with no files at all. If the email text arrived normally, nothing is missing. If you expected a file, ask the sender to send it again as an ordinary attachment.
- Are the files sent to this website?
- No. The winmail.dat is unpacked by this browser tab on your own device, and the attachments you save are written straight from it. Nothing in the file is sent to this site or anywhere else.