You may have noticed once in a while that calendar entries in Exchange are defective in some mailboxes, but Exchange isn't able to repair them with onboard tools. Although you can't fix the problem online, you can use tools for offline repair.

For example, a defective calendar entry in a user mailbox displays in such a way that the user cannot change (edit, delete, or move) it. In addition, the user cannot delete the reminder permanently, even if the appointment is in the past. It therefore always pops up again.

Users are literally helpless because they cannot do anything about these defective entries. The only temporary solution is to push the appointment reminders as far into the future as possible.

This phenomenon occurs both in Outlook's online mode and in Outlook on the Web (OWA). It is therefore not a specific client error.

Users who use Outlook in cached mode can temporarily edit the appointments because Outlook does not constantly check the local copy against Exchange. However, the appointments will pop back up again after the next cache update.

Error messages ^

The following error messages appear:

Sorry, we're having trouble opening this item. This could be temporary, but if you see it again, restart Outlook.""The move, copy, or deletion cannot be completed. The items might have been moved or deleted, or you may not have sufficient permissions. If the item was sent as a task request or meeting request, the sender might not receive updates.

Or simply:

"The item cannot be saved."

The second error message lists missing permissions as a possible cause of the problem. As a first measure, I have therefore checked the permissions of the mailbox folders with:

Get-MailboxfolderPermission

This excludes a faulty configuration here. Even if the users are already the mailbox owners, you can still use:

ADD-MailboxfolderPermission

This grants them the owner rights again.

However, this had no effect on the abovementioned problem; the error messages still remain.

Analysis using free tools ^

The next logical step is to analyze the defective calendar entry to examine the cause of the error. The Microsoft CalChecker tool and MFCMAPI serve this purpose.

Checking the entries with CalCheck showed the following:

The CalCheck tool reports errors, but these do not identify the cause

The CalCheck tool reports errors, but these do not identify the cause

MFCMAPI also found some errors, as the following screenshot shows:

MFCMAPI also detects problems, but the error codes do not allow drawing any conclusions about the cause

MFCMAPI also detects problems, but the error codes do not allow drawing any conclusions about the cause

Unfortunately, there are no causes or useful solutions under these error codes.

Attempting a repair using PowerShell ^

Exchange has some PowerShell cmdlets that could fix a broken calendar entry. One of them is:

New-MailboxRepairRequest

The command is very rudimentary, and it doesn't give any usable feedback from the console. Instead, you have to look at the event log based on different EventIDs. But above all, it did not bring any success.

Another option is to delete the broken entry via PowerShell. The Search-Mailbox command exists for this. During my troubleshooting attempt, it actually reported that the entry in question had been removed. Unfortunately, the reality was quite different because the defective calendar entry was still there.

Export and reimport ^

Microsoft support suggested as a solution that you export the mailbox to a .pst file without the calendar and then disable the mailbox from the Exchange console.

Then you should create a new empty mailbox and import the .pst file without the calendar. However, this is usually not acceptable to users because they depend on their calendar entries.

A better alternative would be to export the mailbox to a .pst file, skipping only the broken calendar entry. You can do this manually or via PowerShell with New-MailboxExportRequest. Getting the right entry when exporting is a bit time-consuming.

Overall, this is a rather complex approach and not a very nice one because you have to coordinate appointments with the users when you can take their mailboxes offline.

Third-party tools ^

In addition to these onboard tools, some utilities from manufacturers also specialize in repairing mailboxes. However, they are not limited to the mailbox, as they are able to read the Exchange database (EDB) as a whole.

The repair occurs in such a way that it makes the data from the offline EDB available in a new mailbox (Exchange Live) or in a .pst (or other local file). Stellar Repair for Exchange from Stellar Data Recovery is relatively widespread and easy to use. After it has scanned the database, it will display its entire contents.

Stellar Repair for Exchange offers the possibility to repair the Exchange database offline

Stellar Repair for Exchange offers the possibility to repair the Exchange database offline

In my test, Stellar was able to fix the entries. Unfortunately, the fact remains that it is not an online repair, thereby significantly increasing the effort.

Restoring from backup ^

Another option and possibly a more cost-effective one would be to take a closer look at your backup program used to back up Exchange and its mailboxes. I use Veeam Backup & Replication for this.

As expected, the backup included the defective entry.

Veeam Backup & Replication is able to repair defective calendar entries correctly upon restoring them

Veeam Backup & Replication is able to repair defective calendar entries correctly upon restoring them

The disadvantage of restoring to an existing mailbox is that Veeam does not overwrite the existing entries there. It instead creates a copy of every original appointment in the calendar.

The surprise here was that the original calendar entry was still corrupt, but the restored version was not. So it seems Veeam resets the entries.

Hence, to repair the entries in the calendar, you can back up the mailbox once with Veeam, disable it, recreate it, and then restore the backup there. The previously defective calendar entries are now intact again, and the user can edit them.

Conclusion ^

Currently, there seems to be no method to fix this error online. You can correct a defective calendar entry offline in several ways, but to do this, you always have to create a new mailbox.

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As the error has only occurred with very few users, the repair effort is still minimal. However, it's not possible to determine the actual reason why these few individual calendar entries were defective (5 out of 6,000).

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1 Comment
  1. Tobias 5 months ago

    I have this exact issue with corrupted calendar reminders and i can confirm that a restore from Veeam fixes the problem. But i must also agree that deleting the users mailbox and do a complete restore of that mailbox is very inconvenient and time consuming.

    But at least i have a solution now 🙂 Thank you for the article.

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