Looking at the email source the for the invitation there's this part (IDs changed, so it's not proper link to test with):

Any thoughts about how to fix this issue?

Patch seems to work. I haven't seen this issue after applying the patch. Thanks a lot!

@machniak Thanks a lot! I'll try the patch. This .ics arrived from Microsoft Exchange Server 2010 (based on the PRODID field in .ics).

Could anyone please review this patch? it sounds like an important fix to have.

Hmm, the user who has been reporting this issue uses some mobile email client in addition to the kolab roundcubemail, so it *might* be related to mobile client, but I'm not sure really..

Any thoughts/plans about fixing this issue? Users hit this issue very often, because currently kolab auto-updates only the *first* recipient calendar..

Any tips how to best debug this issue?

That's the problem. The error in question hasn't happened to me, so i don't know the exact steps to reproduce. What I've heard is that "it just happens automatically". When the recipient gets the calendar invitation email, the placeholder event is automatically created in the calendar (per kolab policy settings), and when the recipient user tries to accept/reject the invitation from the kolab roundcube webmail *calendar* application he gets the Internal Server Error and the PHP Fatal Error and the stack trace I posted can be found from the logs.

I hope I didn't screw up the xml while removing private info.. but here goes:
http://pasik.reaktio.net/kolab-webmail-calendar-internal-server-error.xml

Sorry took a while, but now it happened again..:

Which parts of the XML are important? I can try to find it..

Just in case, more rpm versions:

So the actual issue seems to be if there are multiple recipients in the calendar invitation email then wallaced only creates the placeholder calendar event for the *first* recipient only.

Yes, i'm pretty certain this is the actual issue i've been seeing.

Another test was now done by sending a calendar invitation from Exchange 2010 to Kolab 16.1.

Oh, it seems --debug=8 syntax doesn't seem to work. This works instead:

This seems to be related to what email platform the sender is using. I tested the same procedure using google gmail.com as a sender, and kolab seems to work properly in that case, and updates the not-yet-accepted calendar invitation just like it should.

I accidentally created this as a bug, but it should be a feature request obviously.. and it seems I can't change the type myself?