What Mail Opener does
Open an Outlook .msg, an .eml or a winmail.dat on your phone or computer. Read it and save or share the attachments, without Outlook or uploading.
Someone using Outlook sends you an email as an attachment, or your mail app shows an attachment called winmail.dat or ATT00001.dat that nothing on your phone can open. Those are Outlook's own formats: a .msg is a saved Outlook message, and winmail.dat is how Outlook packs the formatting and the real attachments of an email for mail apps that do not speak its format. Mail Opener reads all three formats, .msg, .eml and winmail.dat, in your browser.
Tap Open email file and pick the file from Downloads or Files. The email appears in a few seconds: subject, sender, recipients, the date in your own time zone, and the body as it was written. The attachments are listed with their real names, and each one can be saved or shared to another app. On a computer you can drop files onto the page.
The file is opened on your device and is not uploaded. The email body is shown in an isolated frame that cannot run scripts, and remote images, which can tell a sender that the email was opened, stay blocked until you choose to load them. An email encrypted with S/MIME cannot be read without the recipient's key, and the tool says so.
Free opens 3 email files a day. Pro is a one-time purchase: any number of files, several at once, all attachments as one .zip, the email saved as a PDF, the email inside an email, and the full headers.
Popular uses
Each opens Mail Opener already set up for that job, with steps and answers for that case.
Free vs Pro
| Feature | Free $0 · no account |
Pro |
|---|---|---|
| Open Outlook .msg, .eml and winmail.dat (also ATT00001.dat) files: the format is recognised from the file's bytes, so a file your phone calls 'application/octet-stream' still opens | Included | Included |
| Subject, sender, recipients and date in your time zone, then the email body as it was formatted, including HTML that Outlook kept only inside an RTF body | Included | Included |
| Inline images in the body; remote images stay blocked until you choose to load them | Included | Included |
| Every attachment with its name, type and size: save it, or share it to Files, Drive or another app where the browser supports sharing; images show a preview | Included | Included |
| Up to 3 email files a day, counted when an email is shown. The built-in samples never count | Included | Included |
| Any number of email files, every day | — | Pro |
| Open several files at once, listed side by side with ↑/↓ to move between them on a computer | — | Pro |
| Save all attachments as one .zip | — | Pro |
| Save the email as a PDF (headers, body text and the attachment list) | — | Pro |
| Open the email inside an email: a winmail.dat inside an .eml, an attached .msg or a forwarded message | — | Pro |
| All headers and the raw properties of the file | — | Pro |
| Always load remote images for senders you choose | — | Pro |
Pro is $9.50 until Oct 25 (then $19), paid once. Checkout and the licence key are handled by Dodo Payments (merchant of record). By buying you agree to the Terms and Privacy Policy.
Questions
Is Mail Opener free?
Yes, with no account and no install. The free plan includes: Open Outlook .msg, .eml and winmail.dat (also ATT00001.dat) files: the format is recognised from the file's bytes, so a file your phone calls 'application/octet-stream' still opens; Subject, sender, recipients and date in your time zone, then the email body as it was formatted, including HTML that Outlook kept only inside an RTF body; Inline images in the body; remote images stay blocked until you choose to load them; Every attachment with its name, type and size: save it, or share it to Files, Drive or another app where the browser supports sharing; images show a preview; Up to 3 email files a day, counted when an email is shown. The built-in samples never count. Pro ($19, paid once) adds: Any number of email files, every day; Open several files at once, listed side by side with ↑/↓ to move between them on a computer; Save all attachments as one .zip; Save the email as a PDF (headers, body text and the attachment list); Open the email inside an email: a winmail.dat inside an .eml, an attached .msg or a forwarded message; All headers and the raw properties of the file; Always load remote images for senders you choose.
Does Mail Opener upload my data?
No. Your email file is opened in your browser and is never uploaded. To apply the free daily limit, the page sends us a count request with a random ID for this browser and a one-way hash of your network address, never the email or its contents; these counters are deleted after 2 days. Remote images inside an email are blocked until you choose to load them (loading them contacts the sender's image servers, as any mail app does). Pro checks your licence key with our licence service. See the Privacy Policy for retention and deletion.
Do I need to install anything?
No. Open the page and start working. It works on desktop and mobile browsers.
How does the Pro licence work?
You pay once and receive a licence key by email from Dodo Payments (our merchant of record). Paste it under "Have a key?" inside the tool. One key works on up to 3 browsers; you can release a browser at any time to use the key elsewhere.
What is winmail.dat or ATT00001.dat?
It is a file Outlook attaches when it sends an email in its own rich-text format to a mail app that does not understand that format. The real attachments and the formatted body are packed inside it. Mail Opener unpacks it and lists the files inside so you can save them.
Can I open a .msg file on Android or an iPhone?
Yes, in the browser. Tap Open email file and choose the .msg from Downloads, Files or Drive. Android often labels these files as generic data; the tool recognises the format from the file itself, not from its name or type.
Why does the body of some Outlook emails look plain?
Outlook can store a body only as RTF. When that RTF carries the original HTML, the email is shown with its formatting. When it does not, the text is shown and the page says it is shown as plain text.
Can it open encrypted emails?
No. An email encrypted with S/MIME can only be decrypted with the recipient's private key, which stays in their mail app. The tool shows the sender and subject and says the body cannot be read. Signed (not encrypted) emails open normally.
Does loading remote images tell the sender I opened the email?
It can. Remote images are fetched from the sender's servers, which is how some emails track opens. That is why they are blocked until you press Load remote images.
