Slingshot Email Upload

I’m using Slingshot GitHub - CulturalMe/meteor-slingshot: Upload files directly to AWS S3, Google Cloud Storage and others in meteor to upload files to an S3 Bucket. It allows for whitelisting filetypes based on MIME.

I’m trying to upload an Outlook .msg file. But it’s not working because the HTML File.type for .msg is actually “”.

I’m trying to avoid a hacky soln of checking the extension (bc client can rename virus.exe to virus.msg)

Was thinking to analyze File Headers or something to detect that it’s actually an .msg.

Any insights or solutions on this?