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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.

XX.XX.XX.XX does not like recipient.
Remote host said: 554 5.7.1 <>: 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?


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Your Problem is not with iCal directly but with your Mail-Server, which is not properly configured. iCal is sending the invitation/confirmation via SMTP, but the Mail-Server of your Host/Internet-Provider is rejecting the mail due to an authentication error - hence the "Relay access denied". For further Information you can lookup the 554-Error in the official RFC-Documentation regarding SMTP (, Chapter 4.2.1. 'REPLY CODES BY FUNCTION GROUPS' Do the Sender and Recipient use the same Mail/iCal-Server? – J.C. Jul 3 '13 at 7:07
"Do the Sender and Recipient use the same Mail/iCal-Server?" No... similar setup two different machines... two different static ip addresses. Question: but doesn't the iCal-Answer-Mail get sent over the mac mail server too? It has the authentication information and has no problems with regular email. – Joseph Jul 3 '13 at 8:48
have a look here and check the configuration of your Mailserver: and – J.C. Jul 3 '13 at 9:19
My server supports "+" addressing. That isn't an issue. I checked the caldavd.plist but it has a completely different structure than the example in your first link. Is a separate user really necessary? – Joseph Jul 3 '13 at 11:04
up vote 0 down vote accepted

This solved it without having to dig into the plist:

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