Can't email zip file with folders

Hello guys,

So here's the problem. If I create a zip with folders in it, I get a

"Cannot send message using the server iCloud

Sending the message content to the server failed.

Select a different outgoing mail server from the list below or click Try Later to leave the message in your Outbox until it can be sent."

error.

If I save it to drafts then go to icloud.com and try sending it from there, it does work.

If I create a zip with just files in it, it works as well.

I can even try and attach an app, or a folder itself, it also fails.

I also tried changing the file's extension, it still failed.

Tried it with several email clients, all failed. The only way to succeed is to save it to drafts and send it from icloud.com.

If I try and send it from my iPhone/iPad after saving it to Drafts, I get a "The server error encountered was: No password provided. Please go to Mail Account Settings and enter a password". But a password is already set.

It doesn't matter how large or small the file is (under 15MB, of course), if it has folders it fails, if it doesn't, it works.