Our teacher taught us to ask for the permission to ask a question by saying「質問してもいいですか。」. Now I'm writing her an email, and would like to say something along the lines of "If I may ask a question, ...", where (...) would be a grammar question, for example.
I would have written 「質問してもよかったら、……」, but Google returns no hits at all for this specific sentence, so obviously it's not correct.
How would you say "If I may ask a question, ..."?