How to minimise apps on startup

I have 3 apps set to "Launch on startup": Mail, Messages, and Skype. All 3 of them have "Hide" on in "Login Items". Skype and Mail ignores "Hide" attribute and every time i log in the windows pop up. Is there any way to prevent Mail and Skype from opening windows when i log in? Browsing online says to mark "Hide" option, but the option is already marked for both applications. Messages.App works as intended, starts nicely in the background.

I also followed this article: https://discussions.apple.com/thread/6727254

Deleted "~/Library/Containers/com.apple.mail/Data/Library/Saved Application State/" manually, however, this worked for one startup, and started messing up later.

Solution 1:

There are times where an application is not built with standard libraries, and as a part of that, those applications may not respect the native OS settings.

This ultimately comes down to how a application was developed.