Why is "wieviele" not recognized as a word in my spell checker?

Question

When I write the word "wieviele" in my German spell checker (Thunderbird), it tells me it is an error:

Although a quick search at linguee.de tells me that it is an often-used word.

Answer 1

"Wieviel" is the alte Rechtschreibung. The modern spelling is "wie viel". "Wie viele" is written as two words, both in the old and new spelling.