Outlook won't open my HEIC attachment
Outlook for Windows can sometimes preview a HEIC attachment, but trying to save, forward, or open it in another app usually fails with 'this file type isn't supported.' The HEIF codec from Microsoft Store only helps the Photos app, not Outlook's attachment handler. Convert the HEIC to JPG and re-attach.
The fix
Convert your HEIC to JPG using the converter on this site. Drop the file, click Convert, upload the JPG to Outlook instead. Conversion runs in your browser — no upload, no signup.
Why this happens with Outlook specifically
- Outlook for Windows uses a private image pipeline that doesn't honor system-level HEIF extensions
- Outlook for Mac handles HEIC natively (it ships with the OS codec)
- Outlook on the web (outlook.live.com) usually previews HEIC but downloads fail in non-Edge browsers
- Mobile Outlook (Android, iOS) varies by version — some can preview, none forward reliably
The long-term workaround
When forwarding an iPhone photo from Outlook to a non-Apple recipient, convert the HEIC to JPG first and replace the attachment. Otherwise the recipient gets a file they can't open and you get a polite reply asking for a JPG.