Outlook - countable or singular noun?

I have a query from a client regarding the use of outlook but I am not sure how to answer her question. Can anyone help me?

"The word is outlook. My Collins Cobuild says that when you use outlook to mean whether something or not is going to be successful, prosperous etc. it is a singular noun and thus takes a singular verb. If you use outlook in the sense your general attitude towards life, it is a countable noun.

Do you have any opinion on the first meaning? I tend to trust Collins, but I've also seen it used with a plural verb. Can you recommend one or the other?"