[Evolution] close original mail after reply

[Carpetnailz <carpetnailz researchintegration org>]

At one point I was prompted whether I wanted to have original mail close
or stay open after replying. I chose 'stay open', but now I want to
chose 'close'. I've looked through all the menu items, particularly
Edit/Preferences, but can't find a place to make that change.

Googling only gives some people wishing there were such a feature. Yet I
was prompted for a choice about it, so there must be such a feature.
Where is it?

Thanks.