winmail.dat is not a real attachment. It is a container file created by Microsoft Outlook for Windows — a format called TNEF (Transport Neutral Encapsulation Format) — that wraps the actual attachments and email formatting inside a single opaque file. When Outlook sends an email to a non-Outlook recipient, the real files end up hidden inside winmail.dat, which Apple Mail, iPhone Mail, and most other email clients have no way to open.

MailRaider unpacks it. Double-click the file on Mac, or tap it on iPhone, and MailRaider opens it immediately — showing you the formatted email and the real attachments that were hidden inside.

If winmail.dat has been saved to your Mac — either downloaded from Mail or copied from another source — double-click it in Finder. MailRaider opens automatically and displays the email content and attachments. You can then save attachments by dragging them from the attachments drawer, or export the email to PDF, RTF, or EML.

You can also preview a winmail.dat file without opening MailRaider at all: select it in Finder and press Space. Quick Look shows the full formatted email content immediately.

When a winmail.dat attachment arrives in the iOS Mail app, tap it. If MailRaider for iOS is installed, it opens immediately and displays the real content. Attachments can be saved from within MailRaider to Files, iCloud Drive, or any other location.

The sender’s version of Outlook is configured to use RTF formatting when sending email. This causes Outlook to wrap the message in TNEF, producing winmail.dat for any recipient not using Outlook. The sender can prevent it by changing their Outlook settings to send in HTML or plain text format — but if that isn’t possible, MailRaider is the solution at the receiving end.

For the full tutorial on opening winmail.dat and other Microsoft email formats on Mac and iPhone — including Spotlight search, Quick Look, attachments, and export — see the complete MailRaider tutorial.