iCal invites are not received by some people (I know why, but Apple won't fix it)
I switched to icloud a while back and have the maddening problem of SOME people not receiving invites, and have discovered what causes it (at least in my case):
If the user you are sending to has an itunes (or apple id) account with that email as the login (and that email is NOT an icloud email) they will never receive the iCal invite! Instead it gets routed to their (non setup) icloud account. If they start using icloud for their calendars with this same external email address as login, they will receive them there (directly on their calendar if it is setup). Apple refuses to forward it to their real email address, the one we are sending it to. I have reported it to Apple several times but they are not inclined to fix it, probably because they want to force external users to use icloud. This is mega frustrating. Many of my friends do not receive invites, forcing me to use Google calendar for events with those friends. I prefer the general interface and look of icloud/ical invites, but I need to be able to actually invite people!😠