[vba] "Sub or Function not defined" when trying to run a VBA script in Outlook

I had a similar situation with this issue. In this case it would have looked like this

Sub Test()
   MsqBox ("Hello world")
End Sub

The problem was, that I had a lot more code there and couldn't recognize, that there was a misspelling in "MsqBox" (q instead of g) and therefore I had an error, it was really misleading, but since you can get on this error like that, maybe someone else will notice that it was cause by a misspelling like this...