Outlook: Issue with modified occurrences in a series

Currently I see an increasing number of reports about missing body of meeting series. As most of the series are Skype for Business and contain the dial-in information, this is really a bad end-user experience. Imagine you want to join the meeting and have no dial-in information or the attachments are gone.

My first thoughts were that this is a Skype for Business only issue or related to Exchange ActiveSync. But this time it turned out it’s not. After analyzing of several cases, it came down to an Outlook for Windows only issue in a delegate scenario.

Update 19.09.2017

The issue was resolved in Version 1706 (Build 8229.2103), which is the July version of the Current Channel. Please be aware about the changes to Office 365 ProPlus update management! You can read more about the changes here. Either way, when you are on Deferred or Semi-Annual Channel you have to wait for this fix.

It took me a while and a lot of meeting series, but finally I’ve found a way to reproduce the issue. First in my on-premises environment, which is currently running Exchange 2016 CU4, and then also in my tenant. After I’ve found the steps, I’ve tested OWA and Outlook for Mac. But there everything worked fine.

From this it seems that only Outlook for Windows is affected. I tested this with Version 1701 (Build 7766.2092), which is Deferred Channel. Therefore I did the same with the Current Channel Version 1701 (Build 7766.2092) and got the same results.

Symptoms

  • On-Premises
    When a delegate has unchecked the option “Download shared folders” and opens or tries to create an occurrence of a series in his manager’s mailbox, the body will be empty.
  • Exchange online
    In this case sometimes the body is shown correctly or the body of the series is shown. The delegate can edit the body and send the update to all attendees. All attendees will receive the occurrence with the modified body, but the modified body of this occurrence is not saved in manager’s mailbox.

Technical background

Every modified occurrence in a series is called exception. All information for exceptions are stored in the MAPI property PidLidAppointmentRecur stored. The ExceptionInfo structure is described here. To view these properties, the best tool is MFCMAPI.

Here is an example

Occurrences_01.png

As you can see there are also information stored, what was changed on a occurrence, similar to PidLidChangeHighlight. I enumerate this property in my script Get-CalendarItems.ps1, which is really helpful to analyze calendar issue.

Occurrences_02.png

The interesting part is where and how these modified occurrences are stored. For each modified occurrence of a series you will find an object in the attachment table

Occurrences_03.png

Occurrences_04.png

Once you have opened the attachment, you will see the meeting. The body is represented in the MAPI properties PR_Body, PR_HTML and PR_RTF_COMPRESSED

Occurrences_06.png

Occurrences_05.png

Occurrences_07.png

On the occurrences, which have the body stripped, these properties are NULL.

Workaround

As this issue exist only when you use Outlook for Windows under the following conditions:

  • your profile is configured for Cached Mode
  • you are a delegate and have your manager’s mailbox added to your profile as described in this KB
  • Download shared folders check-box is cleared

There are the following options:

  • rather to modify an occurrence, delete the one and create a new appointment (which is anyways the preferred and best practise)
  • check Download shared folders

Note: This can cause performance and inconsistency issue as the OST file will grow as Outlook will download all folders, including Calendars, which are checked.

  • use OWA or Outlook for Mac to modify these occurrences

Conclusion

It is fact that meeting series get often changed. It is also well-known that Cached Mode can cause performance issue on clients  as described in this KB article. Or due to used Outlook add-ins.

Thus means the chance you get hit by this specific issue, is extremely high. I can only recommend that changes of occurrences are done by cancellation and creating a new meeting. I’m confident Microsoft will provid a fix for this. I’ll let you know when a fix is available.

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