Avaliado com 2 de 5 estrelas

It makes what claims, but if by mistake you open another window, it will not close...

Esta análise é para uma versão anterior do extra (1.0.0.1). 

This issue has been fixed in version 1.1.0.0, which is awaiting its review by the Thunderbird add-ons team since about a month now. If you don't want to wait for the review, you can download it at https://addons.thunderbird.net/thunderbird/downloads/file/1016729/minimize_on_close-1.1.0.0-tb.xpi