If you're having those problems you may consider using "Create Gift Link" instead of "Send Email" (you should have both options when choosing "Gift to a friend" in the Humble keys page), and then paste the link in the Keys section of the giveaway.
That's what I do at least.
Having said that, yeah, people should check their emails.
Thanks for the GA.

thank you for the giveaway!

Thanks!

ty

Thanks~

Hvala puno!

Thank you so much!!

Thanks!

Thank you for making this giveaway. ^_^

Thanks!

thx a lot!

Thanks mate!

Thanks!!!

I've put a Humble Gift link in a few times where the key goes. I've had a couple issues already of people not checking the email that's associated with their account on here, so I can imagine they probably don't think to check or possibly don't care.

Thanks !

Amazing game, thanks for the giveaway