Today, we’re excited to announce the release of large file attachment support for Outlook messages via the Microsoft Graph beta endpoint. You can now attach files up to 150 MB to a message. As always, message recipients can get the attachment metadata, or get the actual raw contents of the attachment.

We’ve heard you loud and clear that the current file size limit of 4MB for uploading file attachments to Microsoft Graph is a major roadblock. With this API release, you can create an upload session, and iteratively use PUT API calls to upload ranges of bytes of the file until you have uploaded the entire file. This approach effectively removes the 4MB upload limit and helps you upload attachments from unreliable networks.

You can get started today by following the steps in Attach large files to Outlook messages.

Do note that upload sessions should be used for uploading files that are greater than 3 MB in size. For file sizes lower than 3 MB, you can continue to do a single POST on the attachments navigation property of the message.

If you have any feedback or suggestions for these or other APIs, please let us know via the UserVoice forum.

Happy coding!