Shoutbox

I know there is an option somewhere for this because I turned it off last time I updated Messenger, but I can't for the life of me find it again.

Whenever my chat window is minimised, and then I minimise every other window I have open, my chat window will always automatically maximise .  This is NOT 'always on top', but something different.  And it's driving me crazy!

Thanks in advance to those people who take the time to help people like me with tiny questions.