Correct forms are - Are there any questions? - Is there a question? Any is used with plural nouns. See Practical English Usage by Swan (3rd edition, page 46) More examples from English Grammar in Use by Murphy (5th edition, page 138) - Did you buy any apples? (plural countable noun) - Did you buy any apple juice? (uncountable noun) Incorrect is - Did you buy any apple? (<<== should be "Did you buy an apple?") Related but different is - Any X ... (meaning Any one of X no matter which one) ... Practical English Usage p. 47.

Others have given you the correct answer, plural. However, the email you received doesn’t sound too bad and you will hear it pretty regularly. “Do you have a question?” sounds a little more abrupt. Changing “a” to “any” is more inviting and suggests that there isn’t a limit on the type of question you can ask. You could also hear “There isn’t any question that we need to replace the old servers promptly. Our survival depends on it. “

It should be singular because of "any". However, in speech, we always hear it in plural. We don't correct others of their speech errors to embarrass them unless you are the teacher.

Questions!

It's questions.