I don't know where this group stands on the email invitation front, but from my understanding of reading this list and several other websites 1) Calendar Server is able to send email invitations and receive replies (both to internal and external users) 2) Receiving External request is still not working (i.e. My wife has Groupwise at her office and I have to drap-and-drop invitations from my mail account into my caldav calendar...it doesn't notify me of a new request) I ran across this website and it looks promising. I just don't have the knowledge, skill or understanding of working with postfix/dovecot etc. http://www.doughellmann.com/articles/pythonmagazine/features/mailbox2ics/ind... After reading this...the idea of replicating the user "com.apple.calendarserver" from apple's implementation makes since if the user has the proper permissions on the email side. My understanding from reading web page.... 1) com.apple.calendarserver would connect IMAP or POP 2) based on having read-access to all users mail folders...perform a general search looking for Caldav info related emails 3) parse the info and scan the UID database in Calendarserver based on the "CUADD field"... 4) deliver to /inbox Anybody want to comment or help?