Not really a bug but by some reason every e-mail service out there is blocking e-mails from our dofgame.com server that sends out these e-mails. We found a way to register it with major sites like gmail, hotmail e.t.c so towards end of the week, or possible early next week situation should improve.
Meanwhile - just e-mail to firstname.lastname@example.org
with all the friends invited (and their in-game username) and we`ll send these e-mails out manually.
And thank for supporting DoF and inviting your friends!
Oh and I think we already sent Kiroy his bonus keys this morning.