CalDAV support for attachments

[ewilen]

Both ZWC and Outlook via ZCO support (adding/reading) attachments as part of an appointment. I just noticed that iCal doesn't allow this for events on a Zimbra CalDAV calendar, although it does for a calendar located "on my computer".

iCal claims it has this ability (iCal 3.0.6 help, "Attaching a file to an event invitation", specifically mentioning CalDAV). And the CalDAV RFC mentions the capability, too: RFC 4791 - Calendaring Extensions to WebDAV (CalDAV), section 8.5

So is this a limitation of Zimbra CalDAV, or does iCAL actually depend on some funky stuff that's only in iCal Server?

[et01267]

Any update on this issue? I don't seem to be able to save a URL as an attachment to an event. Well, I can create such an attachment in ZCS, but the attachment does not make it to my desktop calendar when sync'd via CalDAV. This is using either Lightning or iCal.

[MaSch]

I just tried the same and I am missing this feature too. It would be especially cool if External Attachments ( RFC 4791 8.5.2 ) were supported. So that one could place "clickable" URLs (http or local ones with file) in the attachment fields.
This would allow much higher efficiency.

[ewilen]

Even in Mac OS X 10.7 Lion with ZCS 10.7, I find that I can only add an attachment to an event if it's on a local calendar.

Bug 38212 – CalDAV iCal add attachments feature not visible suggests that iCal might be able to handle attachments with some servers, but Zimbra works in a way that isn't compatible with iCal's method.

Strangely, discussion no Apple's forums (e.g. https://discussions.apple.com/thread...rt=15&tstart=0) suggests that this feature used to work with Apple's MobileMe, but then stopped working when MobileMe was upgraded.

However, iCal's own help (search on "attach a file to an ical event") still explains how to attach a file.

I suspect that if Zimbra had the right hooks, then RFC 4791 8.5.2 would still work with iCal. Zimbra is a WebDAV server, so in theory it could accept the files from iCal and host them. But off the top of my head, there are some problems. First, both ZWC and Outlook use inline attachments (RFC 4791 8.5.1). Second, if Zimbra is hosting the files, you need a way for external users to access them. That adds complications regarding file security, configuring access, and managing the files after the meeting is over.

[MaSch]

hmmm too summarize, the way I understand the whole thing :

Zimbra only supports "Inline Attachments"
iCal and Mozilla Thunderbird / Lightning only support "External Attachments"

As far as I understand the RFC this is good for Zimbra in way because they provide the required feature to conform to CalDav ("CalDAV clients MUST support inline attachments ... . CalDAV servers MUST support inline attachments).

Funnily if this is the case then I wonder, why Apple isn't properly supporting their own RFC requirements in iCal. For Thunderbird/Ligthning there has been an according Bug Report open for 9 years now Bug 168680 however, work on this now seems to be progressing in the last few months, so we hopefully have compatibility there soon)

Another possibility would be Zimbra adding support for external Attachments (rfc4791#section-8.5.2) too, so that it would work at least in this way with the clients existing capatibilites. However this seems unlikely as this Zimbra Bug is marked invalid. Even though I'm not sure why, because the way I read the RFC, inline and external attachments are not mutually exclusive ?!

[ewilen]

That is a good point about the RFC. A report filed at Bug Reporting - Apple Developer is about the only way to try to get the message across. I'd note, though, that things are gradually changing in the CalDAV world to become more "server-centric". While draft-desruisseaux-caldav-sched-09 - CalDAV Scheduling Extensions to WebDAV doesn't have much to say about them directly, the thrust of the draft RFE is, I believe, to let servers do more of the work. "External" attachments arguably make more sense in this paradigm.

[andy204]

to be honest, this is really a problem since apple ical deletes the attachments on the zimbra server. it doesnt matter for me who is guilty, this is not useable.

[andy204]

vote here: https://bugzilla.zimbra.com/show_bug.cgi?id=64747