Here's the ground rules:<p>The customer has just signed up to trial your new app or web service.<p>1 - You have to ask the question in email.
2 - It can't be offensive or unprofessional etc.
3 - It must get them to reply and start a dialogue.<p>What question would you ask to get highest % reply rate?
I'd research the person via the provided name and/or email and then use your gut feeling to ask a question that is a) interesting to the recipient and b) shows you've put time in and this isn't a random mail.<p>E.g. you find the person on LinkedIn and find out the company they're working for is in an industry you don't know well. Tell them that you've researched they work in that industry and that you'd like to know what specific problems they're facing and want to solve in order to know how to improve your software.