Mac appsIn development · reservations opening soon
Kaifu
Open the winmail.dat that came from Outlook with a double-click
$12 one-time (no subscription) · macOS 14 Sonoma or later (planned)
What it is for
Some emails sent from Microsoft Outlook arrive with one attachment called winmail.dat instead of the files the sender attached. The files are inside it, packed in Microsoft’s TNEF format, and Mail on Mac does not always unpack them.
Kaifu opens a winmail.dat with a double-click, lists the files inside, and lets you save them where you want.
It is built natively for Apple silicon, so it keeps working with macOS 28, when Rosetta for Intel-based apps becomes limited to certain older games (Apple Support: Using Intel-based apps on a Mac with Apple silicon).
Features (planned)
Open by double-click or drag and drop
See the attachments inside a winmail.dat with name, size and type.
Save one file or all of them
“Save All” to a folder, or drag a single file to Finder or another app.
Read the message text
Shows the plain-text or rich-text body when the sender’s message included it.
Quick Look
Press Space on a winmail.dat in Finder to see what is inside without opening the app.
File names as the sender wrote them
Decodes names stored in Unicode and in older code pages, such as Japanese Shift_JIS.
Stays on your Mac
No upload, no account, works offline. Universal app: native on Apple silicon, also runs on Intel Macs.
Planned price and reservation
| Planned price | $12 one-time (no subscription) |
|---|---|
| Founder reservation | $4, deducted from the price; fully refundable at any time before release |
| If you reserve | $8 at release for founders |
| Requirements | macOS 14 Sonoma or later (planned) |
Reservations have not opened yet. Join the waitlist below and we will tell you when they do.
Waitlist (email only)
Get one email when Kaifu is released and when reservations open.
Used only to tell you about the release and reservations. Privacy policy
FAQ
- Does it open .msg files?
- Not in the first release. Outlook .msg files use a different format. If many people on the waitlist ask for it, it will be considered.
- Is Kaifu related to Microsoft?
- No. Kaifu is an independent app. Microsoft and Outlook are trademarks of the Microsoft group of companies.
- How is it different from other winmail.dat apps?
- Some Mac apps for this job have not been updated for years and run only as Intel-based apps through Rosetta, which will stop opening them with macOS 28. Kaifu is a new app, native on Apple silicon.
- Can I buy it now?
- Not yet. The app is in development. You can join the waitlist (email only) or, once reservations open, reserve a founder licence.
- What does the founder reservation include?
- You pay $4 now. The $4 is deducted from the price of the first paid release, and you get the licence key by email on release day.
- Can I get my money back?
- Yes. Until the first release you can ask for a full refund at any time by replying to the receipt email. If the app is cancelled, every reservation is refunded in full.
- How will it be distributed?
- As a direct download, signed and notarized by Apple. A Mac App Store version may follow later.