Mailspring spellcheck seems to automatically recognise the language after a few words, as it says in the settings, but it still marks some of the first words as incorrect, although they aren’t. When right-clicking on a word, the same word is the first in the suggestions. The read underscoring disappears when either right- or left-clicking on the word, but reappears again after clicking somewhere else. The issue doesn’t seem to depend on the language, I can confirm it for English and German.
