Apple Mail is creating its own Space

Up until today when my MacBook Pro booted up, Mail opened up in Space 2 of 9 spaces. All of a sudden now when Apple Mail opens up, it creates its own space (10). It is listed on the Spaces2 dropdown from the menu bar. But as far as I can see there is no hot key to get there. In preferences it is still listed as supposed to open in Space 2. I’ve tried rebooting the machine, closing the Mail program and reopening it, quitting Spaces2 and restarting it, nothing seems to work. When I go to Space 10 (which is only created when Mail opens) there is no top menubar unless I move the mouse to the top of the screen. I’m using Yosemite and just increased my internal RAM from 8GB to 16GB if that is a factor. I would like to know how to get it back to where I only have 9 spaces and Mail opens up where it belongs. Any help would be appreciated.

Sounds like Mail has gone into full screen mode. Move your cursor to the top of the screen so that the top bar shows, and press the green button on the left to exit full screen mode.

thanks, that did the trick.