overnight my Outlook spell check changed to Spanish (Portugal)?

overnight my Outlook spell check changed to Spanish (Portugal) - for the 25 years I have been using computers it has always been USA English. how do I change it bask to English?

?2016-05-23T12:34:51Z

Considering PORTUGUESE is spoken in PORTUGAL, that's a really screwed up Outlook install!.

https://www.extendoffice.com/documents/outlook/2372-outlook-change-default-language.html