some ideas
1. maybe email back you are not in a position to offer the name for sale at this time and send them the part of policy thats says 6 months rule.
You could push the boundry and email them the date you could look at it again ( say 7 months from your reg date)
2. "Thanks for your interest in domain name. At this point in time we are not interested in selling the domain name"
3. keep their email and contact them after the 6 months expires if you so wish...
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Dont be tempted to try and sell it within the 6 months.. It might be a trap to get the name deleted for policy breach by someone who wants it
.. Yes this happens