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In my daily work I communicate with a lot of people in my company that I have neither encountered in person nor heard them on phone. The conversation is usually e-mail or online chat. Some of them have ambiguous first name. I would like to know if they are male or female so I know if I should refer to them as "he" or "she" when talking to other members of my team (for example explaining conclusion of the communication with the person). Is there a preferred polite way how to ask?