When the anime starts and until episode 8, they attached a cell-phone to the phone-microwave and sent a message to that specific phone to trigger sending D-Mails. But in episode 8
Ruka sent a D-Mail to her mother pager
and then in episode 9
Faris sent a D-Mail to (probably) herself
So I'm wondering if there is a plot whole somewhere in the story, or did they figure out a way to send D-Mails from any phone to any phone?
As a side question previously it was mentioned that how they can set D-Mail's time of Arrival:
each second on Phone-Microwave meant an hour going back, so I'm wondering how did they manage to set microwave time to 87600 (10 years)?