FreeNo account, no upload, no app

Open winmail.dat files.

Read the email and save the attachments trapped inside a winmail.dat file, on a Mac, a phone or any PC, without Outlook.

Nothing uploadedAttachments recoveredWorks on phones
DAT

Drop your winmail.dat here

or choose it from your computer. It is read in place and never leaves your device.

Read on this computerUp to 512 MBWorks offline
Opening… Unpacking the message. Your file stays on this computer.
DAT
Read on this computer
Convert
    How to open winmail.dat

    Three steps. Nothing to install.

    1

    Save the winmail.dat

    Save the attachment from the email to your computer or phone. It may also be called ATT00001.dat or untitled.dat.

    2

    Drop it here

    The email inside opens with its sender, date and text, even when it was written in Outlook's rich text format.

    3

    Save the attachments

    Click each file to save it with its real name: documents, PDFs, spreadsheets and pictures.

    Stop getting them

    How to stop winmail.dat for good.

    If you send with Outlook

    1. Choose File › Options › Mail.
    2. Under Compose messages, set Compose messages in this format to HTML.
    3. Under Message format, set rich text messages to Internet recipients to Convert to HTML format.
    4. Send again: the attachments arrive as normal files.

    If one contact still gets it

    1. Outlook can remember rich text for one address.
    2. Start a new email and type the first letters of the address.
    3. Remove it from the suggestions with the X next to it.
    4. Type the full address again and send.

    For Microsoft 365 admins

    1. Connect to Exchange Online PowerShell.
    2. Run Set-RemoteDomain Default -TNEFEnabled $false
    3. Mail to outside domains is then sent without TNEF.
    4. Allow up to an hour for the change to apply.
    What is winmail.dat?

    An Outlook email inside an attachment.

    winmail.dat is how Outlook and Microsoft Exchange pack an email written in their rich text format (RTF) for the Internet. The formatting, and often every attachment, goes into one file in Microsoft's TNEF format. Outlook unpacks it without anyone noticing. Apple Mail, Gmail, Thunderbird and phones cannot, so the person receiving it sees only a winmail.dat, sometimes named ATT00001.dat, and the PDF or spreadsheet they were sent seems to be missing.

    Nothing is lost: the files are inside. This opener reads the TNEF format in your browser and shows the email with its text, sender and date, and every attachment with its original name, ready to save. Emails attached to it open too, as Outlook .msg files you can read in the MSG Viewer.

    If you keep getting winmail.dat from the same person, the steps above stop it at the source. For a whole folder of saved Outlook emails, MSG to PST puts them into one Outlook data file.

    Private by design

    Your mail stays on your computer.

    The viewer is our mail engine running inside this browser tab. It reads the file from your disk, and no copy of your mail is ever made on a server. It also opens Outlook PST and OST files, and any of the other formats, whichever page you drop them on.

    Attachments with their real names
    The email's text, even rich text (RTF)
    Sender, recipients and date
    Emails attached inside it
    ATT00001.dat and untitled.dat
    Files up to 512 MB
    Formatting of rich text emails (shown as plain text)
    Meeting details in calendar invitations
    FAQ

    Winmail.dat Opener questions.

    What is a winmail.dat file?

    It is an email from Microsoft Outlook or Exchange packed in Microsoft's TNEF format. It holds the message's formatting and usually its attachments, which mail apps other than Outlook cannot unpack.

    How do I open winmail.dat on a Mac?

    Save the winmail.dat from Apple Mail, then drop it on the opener above in Safari, Chrome or Firefox. The email and its attachments appear, and you can save each attachment.

    How do I open winmail.dat on an iPhone or Android?

    Save the attachment to Files or Downloads, open this page in Safari or Chrome on the phone, tap Choose winmail.dat and pick the file. It is read on the phone itself.

    Why did I get winmail.dat instead of the attachments?

    The sender wrote the email in Outlook's rich text format, or their Exchange server is set to send it that way. Outlook packs everything into winmail.dat, which only Outlook unpacks by itself.

    Is winmail.dat a virus?

    No. It is a normal Outlook format. The files inside can be anything, though, so treat them like any attachment: open only what you expected from someone you know.

    Is my file uploaded?

    No. The engine runs inside your browser tab and reads the file from your device. Nothing is sent to a server, and it works offline.

    How do I stop receiving winmail.dat?

    Ask the sender to send in HTML: in Outlook, File › Options › Mail, Compose messages in HTML, and convert rich text to HTML for Internet recipients. A Microsoft 365 admin can turn TNEF off for all outside mail.

    Next steps

    Need to do more with it?

    MSG Viewer

    Open the Outlook emails attached inside.

    ViewMSG

    EML Viewer

    Open a saved .eml email.

    ViewEML

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    See who really sent an email.

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