Can't change editor options in outlook.com mail and disable spell check

Since a few days, I cannot change "editor" options while composing mail. The option is disabled:

Also, spell check, what was disabled, has been enabled automatically without asking me.

This is really frustrating, because when I write mails in other language different than English the spell check underline and mark all words as incorrect, and I cannot disable (or change) this option. This makes writing mails a real pain.

I have tried in both Firefox & Edge, neither let me edit the Editor options.