The Asset Manager has only a few MIME types configured so this task is to review and update that configuration.
See the method _getConfiguredFileTypes() in Config.cfc
One specific type that has come up before is SVG.
svg = { serveAsAttachmemnt=false, mimeType="image/svg+xml" }
I needed mp4 video files and defined it in my own Config.cfc. This could be a candidate as well:
settings.assetManager.types.video.mp4 = { serveAsAttachment=true, mimeType="video/mp4" };