I'm kinda new to these giveaways, and I have a question

Yeah. That, or send him an e-mail.

Remind him to mark it, otherwise, report it to support I think. Check the FAQ on that last thing, not 100% sure

Or be patient. He might check it later. Apparently you posted a key to his e-mail, so he might have not logged on the site. If I were you, I'd wait a couple of days and then eventually ask him.

I hope it won't come to that, but if he ignores you for too long, it might be a good idea to report the incident to support.

when you post a key to his email you should have reminded him to click receive after activate it. that's what i do.

I THINK that if he doesn't click "I received", the site marks it as received automatically...
I might be wrong, but on one of my giveaways it took several days to become "received", I believe that was automatic.

EDIT: Of course you have to mark it "sent" in your list

I prefer to do all gifting over chat, so you can make sure people remember. Does mean dealing with timezone differences though. Still waiting for 4 people from my last giveaway.