The specific requirement for being whitelisted is that it shouldn't have a MIME type that Chrome wants to open inline. Give me a list of extensions that you'd like to see supported and I'll see what I can do.

Screensavers are just special exes on Windows and are commonly used as viruses. Might be better not to whitelist that one and instead convince people to zip them up if they really want to send them.

I think that there are a fair number of mail filters that block .scr entirely, anyhow. In that respect, they're similar to .bat, .vbs, .wsh and the like.

Alternatively, you can just offer to automatically zip those for the user. Actually, that might be a good idea for all unrecognized files because it avoids a lot of weird problems with funny extensions that are automatically blocked.

Feel free to use that idea.

gmail does not allow executable attachments - even when zipped, it will inspect the inside of the zip file and reject the executable.

As a developer who sometimes have to send a zipped project with a compiled build inside, I find this "feature" extremely annoying. I usually end up renaming the file from .zip to .lol or similar.

Switch to 7zip. It is more efficient than zip and it passes through Gmail fine and you then don't need to worry about renaming files

Thanks for commenting here. Would HTML or JS attachments be whitelisted?

No, since they can be opened inline.

Is it wise to pursue a whitelist approach?