I would also like this. I’m currently working with a workaround that has large drawbacks.
I have one computer that I use obsidian on most commonly, I wrote a script that gets executed every now and then to download new emails and copy them into my obsidian folder tree. In essence, using the filesystem as an API.
I believe this would be easier if you synced your obsidian vault with a service like Dropbox because you can then use their API, although this gets into really cumbersome territory quickly.
It works fine, but it’s a big drawback that you’d either have to replicate this script on all of your devices or have one device on (or a server) that runs this intermediary all the time.