Hi,

I work for a company, which has around 20.000 mailboxes. A few weeks ago I had a case of a user unable to open occurrences of some series.

After a long troubleshooting we found out the following:

Using MFCMAPI we discovered that some appointment series where showing a wrong message class:

It should be IPM.appointment and not IPM.Appointment.SMIME

This seems to be caused by the fact the user has the setting "Add Digital signature to Outgoing messages" enabled in the "Encrypted e-mail" setting pane.

Resolution:
- Use MFCMAPI to change the class from IPM.Appointment.SMIME to IPM.Appointment
- Disable the "Add digital signature to outgoing message

Once those two steps are done, user is then again able to open the occurrences in the "corrupted" series.

After this incident, I enabled the same functionality on my mailbox (I only use Outlook 2013 and Outlook on windows 8.1 phone. Our mailboxes are on Exchange 2013 on-premises ). After 15 days, I also started to have "corrupted" series for which I could not open occurrences anymore and MFCMAPI showed message class IPM.Appointment.SMIME for those.

My question to you is, has anyone of you had a similar issue? Were you able to resolve it, while leaving the "Add digital Signature to outgoing message" enabled?

Additional information:

- Calcheck shows the following for the series: "WARNING: Message Class (IPM.Appointment.SMIME) is not standard for Calendar item.
- Calcheck is unable to repair the error automatically
- Used the "New-MailboxRepairRequest" with the 4 tasks, it was unable to repair the issue
- Also we disabled the automatic repair function of Exchange 2013 mailboxes, corruption still occurs for some new or ancient meetings
- We verified, and confirmed that on the calendar general tab, the setting is correctly set to IPM.Appointment for the "When posting to this folder, use" option
- We tried with and without "cached mode", corruption still arise
- In OWA, the meetings are working fine
- We tried to use scanpst on the OST but it was unable to resolve the errors
- We removed the OST and started again from a fresh profile, corruption was still present
- We tried on a clean laptop, fresh image (thinking about Office issue), corruption still occured
- Our digital certificate for signing emails are coming from AD

Thank you for your help or suggestions in advance.

Hello Funkjamin,

Thank you for sharing the solution with us.

As a best practice, we normally don't get the calendar items encrypted, its only the emails that we can encrypted.

Thanks,

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Hi Simon,

Thank you for your response. However I think that's the point of my question. Why did those calendar items become encrypted ( IPM.Appointment.SMIME instead off IPM.Appointment) in the first place?

As you say, calendar items should not be encrypted, so why did Outlook 2013 change their class to .SMIME?
Would this be a product bug?