Why did I receive a winmail.dat email attachment?

When you receive an email with an attachment named “winmail.dat”, it can be frustrating. Let’s break down why this happens and what you can do about it:

1. What is the “winmail.dat” file?

   • The “winmail.dat” attachment is a product of Microsoft Outlook’s proprietary RTF (Rich Text Format). When people send messages from incorrectly configured Outlook email clients, this file may be added as an attachment to the message.

   • The winmail.dat file contains formatting information for messages that use Microsoft’s TNEF (Transport Neutral Encapsulation Format) standard and any attachments sent with the original message ¹².

2. Why does it happen?

   • The issue arises because the sender’s Outlook settings are incorrect. Other mail clients (except Outlook or Exchange Client) cannot decode these TNEF-encapsulated attachments.

   • Some webmail services (like Outlook Mail or Gmail) can handle these attachments, allowing you to download them from there ¹.

3. How can you handle it?

   • While there are free utilities available online that can decode winmail.dat files, here are some steps you can take:

     • Ask the sender to adjust their settings: Encourage the sender to stop using a format that recipients can’t easily open. RTF should primarily be used within corporate environments or when the recipient is also using Office Outlook.

     • Check your Outlook settings:

       • Go to File > Options > Mail.

       • Ensure that the compose messages format is set to HTML.

       • In the message format section, make sure that when sending messages to internet recipients, it is set to Convert to HTML format.

       • Close and reopen Outlook, then send yourself a test email with a PDF or picture attachment to check if the issue persists ¹.

Remember, the long-term solution lies in encouraging senders to use formats that are universally accessible. If you encounter this issue frequently, consider reaching out to the sender and explaining the situation.