How do I change the default e-mail in ical for e-mail notifications?

My ical e-mail notifications are set up to my .mac account, but I need to change it to icloud address, as I'm getting errors when it tries to send e-mail notifications to the @mac.com address. But I can't figure out how to change the e-mail address. I've added the icloud.com address in accounts, but it doesn't offer me the choice of that e-mail in the drop-down menu in ical when I choose e-mail notification.