Problem with iCal invitations I have noticed a problem with iCal invitations.

When I recieve an invitation (via email) it pops up in my calendar. I then click it to say accept. When I do my calendar shows that I have accepted, but the person who sent me the invitation does not see my status. 

In addition I get an error Mail with the following error. 

&lt;com.apple.calendarserver+2594a782-bbe9-4385-8ea7-239172296549@MYSERVERNAME.com&gt;:
XX.XX.XX.XX does not like recipient.
Remote host said: 554 5.7.1 &lt;com.apple.calendarserver+2594a782-bbe9-4385-8ea7-239172296549@MYSERVERNAME.com&gt;: Relay access denied
Giving up on XX.XX.XX.XX.


Both sender and recipient are using OSX Lion Server as Mail and Calendar servers and the standard calendar/mail app. With static IP-Adresses. Does iCal need a special port to be forwarded? Or do I need to set some flag in postfix's configuration so that iCal mails are relayed?

The servers relay outgoing mail through a separate host which requires authentication. Could it be that iCal does not use the authentication when it tries to relay the message?

Thanks
This solved it without having to dig into the plist: http://www.dummies.com/how-to/content/how-to-enable-email-invitations-in-lions-ical-serv.html