how to exit full screen mode mail message

Inexplicably, when i open messages in Mail, they appear in something like full screen mode. The message viewer window is not in full screen mode, but if i open any message, the message takes up the whole screen. I can drag the message in order to see other things on the desktop, but i can't adjust the size of the window to the size i want, and see no way of exiting full screen mode. I lookd in Help, but it only shows how to enter Full Screen, not how to exit it.

In the View menu, there is an option to enter full screen. When i have the full screen sized message open on top, the enter full screen option in the View menu is greyed out. If i have the normal sized window for the message viewer window on top, the enter full screen is not grayed out and could be selected. I do not select it since there appears to be no 'exit full screen' option that i can see and i don't want to multiply this problem.

I know this might be a silly question, but if they have an enter full screen option, why wouldn't they also have an exit full screen option?

Or is there an exit full screen option which exists somewhere that i have not been able to find? I've searched Apple Discussions and Google but so far have not found a way to un-full screen my Mail messages. This started this morning.

Can anyone help?

I do not know how it got into full screen mode. It was not something i did deliberately or knowingly.

i have tried quitting and restarting Mail but the full screen message mode returns.

How can i get my mail messages out of this very annoying and awkward screen hogging mode?

I have only been using Mail since last November when i got a new MBP with Mountain Lion, which meant that for the first time since 1995, i could not use the simple straightforward faultless Eudroa anymore. So i have had my struggles with Mail. Trying to get through it. This is the most recent of various similar issues, inexplicable problems without apparent solutions. Sort of Microsoft-like.

I will be really grateful for any help.. thanks