Overview

Users are getting an email message from Kerio Outlook Connector regarding a synchronization issue. The following error on the message is displayed:

Email Subject: Unable to synchronize a message!
Message:
Kerio Outlook Connector hasn't been able to deliver the message.

We are sorry, but an error occurred while synchronizing the <email_data> message from the server to your Outlook account. This is usually caused by an error in the message, but there may be a bug in the product too.
The original message can be found in the Failed Message.eml attachment and you may succeed in opening it. You can also use Kerio Connect Client to access the message.

Environment

Windows 10

Solution 1

On KOFF PC

1. Remove Outlook profile.
2. Remove KOFF and Kerio Updater service.
   If the process failed to uninstall, use the KTUninstall tool to remove unnecessary files.
3. Remove the following folders:
   • C:\Program Files (x86)\Kerio\UpdaterService 
   • C:\Program Files (x86)\Kerio\OutlookConnector 
   • C:\Users\<user-name>\AppData\Local\Kerio\Outlook Connector
4. Reboot PC.
5. Run Office online repair.

On Kerio Connect server

1. Stop Kerio Connect service.
   • Alternatively, go to Start > Run and type services.msc -> stop Kerio Connect.
     
     
2. Navigate to the Store folder.
   Default folder location:
   • Windows: C:\Program Files\Kerio\MailServer\store\mail\[domain]\[username]
   • Linux: /opt/kerio/mailserver/store/mail/[domain]/[username]
   • macOS: /usr/local/kerio/mailserver/store/mail/[domain]/[username]
3. Remove the folder: __keriomapi__STORE
4. Remove the files: .journal.db and specguid.fld 
5. Start Kerio Connect service.
6. Re-index the user's mailbox.
   

On KOFF PC

1. Install KOFF.
2. Re-create Outlook profile.
   

   If the issue still persists, please continue troubleshooting with Solution 2.

Solution 2

Uninstall Microsoft Office Desktop Apps including the preinstalled My Office app in Windows 10.
NOTE: This step also resolves some Signature problems in Outlook.

Caution: we received confirmation from users, that resetting (reimaging) the Windows OS resolved this error. Please perform this procedure as the last resort.

Confirmation

Users should not receive the synchronization message anymore. All email messages, calendars, etc. should now be synced in Outlook.