Winmail.dat Viewer | Open Winmail.dat Online

Winmail.dat viewer that opens TNEF files from Outlook in your browser. Extract the hidden attachments, read the message body and save each file. No upload.

Also known as: winmail.dat viewer · winmail.dat opener · open winmail.dat file online · winmail.dat extractor · winmail.dat reader · tnef viewer · tnef file extractor · extract attachments from winmail.dat · open winmail.dat on iphone · open winmail.dat on mac

email tools

file converters

viewers

Winmail.dat File

Drop a winmail.dat, ATT00001.dat or .eml file here, or click to browse.It is read in your browser and never uploaded.

Message and Attachments

The attachments hidden in the winmail.dat, the formatted message text, and every TNEF attribute and MAPI property will appear here.

About Winmail.dat Viewer

A winmail.dat viewer is used to open the winmail.dat or ATT00001.dat file that Outlook sometimes sends in place of the real attachments, so you can get the files and the formatted message back without Outlook. This one reads the TNEF file in your browser, lists every attachment with its original name, rebuilds the HTML body from Outlook's compressed RTF, and saves the files one at a time or as a ZIP.

Key Features

Extracts every attachment with its original long file name, type, size and dates, one at a time or all together as a ZIP
Rebuilds the formatted HTML message from Outlook's compressed RTF, with inline images shown in place
Opens emails attached inside the winmail.dat and converts them, or the whole message, to .eml for any mail app
Reads winmail.dat, ATT00001.dat and .tnef files, and pulls the winmail.dat out of a saved .eml message
Checks every TNEF attribute checksum and lists the MAPI properties, so a damaged or cut-off file is flagged instead of failing silently
Flags risky attachment types such as .exe, .js and double extensions before you open them

Use Cases

Get the PDF invoice a vendor's Outlook sent you as winmail.dat when you read your mail on an iPhone, iPad or Mac
Recover a signed contract or W-9 that arrived in Gmail as ATT00001.dat instead of a PDF
Read the formatted message a client sent from classic Outlook when Apple Mail shows only winmail.dat
Triage a winmail.dat reported to your help desk without opening Outlook, checking the attachments for risky types first
Inspect the TNEF attributes and MAPI properties that your Exchange, Microsoft 365 or mail gateway integration produced

Supported Formats

winmail.dat and ATT00001.dat (TNEF)

.tnef and application/ms-tnef attachments

.eml messages that carry a winmail.dat part

Emails attached inside a winmail.dat, nested up to 8 levels

HTML, RTF and plain-text message bodies

Related Keywords

winmail.dat viewer

winmail.dat opener

open winmail.dat file online

winmail.dat extractor

winmail.dat reader

tnef viewer

tnef file extractor

extract attachments from winmail.dat

open winmail.dat on iphone

open winmail.dat on mac

What is a winmail.dat file and why did I get one?

Outlook packages a message in Microsoft's Transport Neutral Encapsulation Format (TNEF) when it is sent in Rich Text format, or when an Exchange or Microsoft 365 server decides the recipient can read TNEF. Mail apps that cannot, including Apple Mail on iPhone and Mac, Gmail and Thunderbird, show the package as winmail.dat or ATT00001.dat instead of the attachments and formatted text inside it. Nothing is wrong with the file: open it here to get everything out. To stop it at the source, the sender can switch Outlook to HTML or plain-text format, and an Exchange or Microsoft 365 admin can turn TNEF off for outside domains with Set-RemoteDomain -TNEFEnabled $false.

Is it safe to open a winmail.dat file here?

The file never leaves your browser: it is parsed locally and nothing is uploaded. The message body is shown in a sandboxed frame that cannot run scripts, a Content Security Policy blocks network requests, and remote images stay off until you load them, so tracking pixels cannot tell the sender you opened it. Attachments are saved only when you click download, and they are never opened.

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Frequently asked questions

What is Winmail.dat Viewer used for?

Winmail.dat viewer that opens TNEF files from Outlook in your browser. Extract the hidden attachments, read the message body and save each file. No upload.

Is Winmail.dat Viewer free to use?

Yes. Winmail.dat Viewer is completely free with no usage limits, and there is no paid tier required to use it.

Do I need an account to use Winmail.dat Viewer?

No. Winmail.dat Viewer works immediately in your browser with no signup, login, or email address required.

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