Kerio Outlook Connector (KOC) search function may become slow, causing Outlook to stop responding, freezing, or hanging. When performing entire mailbox search actions, it can load slowly and cause Kerio Outlook Connector Offline Edition and Outlook crash.
Synchronization, opening, and searching particular big mail folders might also cause slow Outlook response and freeze. Disk space problems on a Terminal server might be a sign of local Cache folder corruption.
System Requirements and Antivirus
The Kerio Outlook Connector Offline Edition (KOFF) runs a separate executable program called KoffBackend.exe. This program performs much of the caching of data from the local email database. On a large mailbox, this process may consume upwards of several hundred megabytes. It is recommended for the computer using KOFF to have at least 4 GB of RAM.
PC running on SSD to run KOFF smoothly. KOFF caches and stores the emails locally and having SSD improves the overall performance.
As KOFF is modifying the user's PC folders, it is advisable to exclude the following folders from the local Antivirus software check:
- C:\Program Files\Kerio\Outlook Connector (Offline Edition)
- C:\Program Files (x86)\Kerio\UpdaterService
- C:\Users\<username>\AppData\Local\Kerio\Outlook Connector
For slow search issues, Engineering released improvements in the 9.2.11 version, which mainly affected x64 installations. Please ensure your Kerio Connect and KOFF are upgraded.
Disable 'Group by' View and Outlook Instant Search
In Outlook 2003 and above, there is an option to show emails in groups. If you find that folders (such as the Sent Items) take an excessive time to load, it is recommended to disable the 'Group by' view, which is the view option Show in groups.
In Outlook 2007, there is an instant search option that can cause slowness in Outlook with KOFF. We have noticed significant improvements after disabling the Outlook instant search feature.
Filter rules that move items to non-standard folders may cause reduced or sluggish responsiveness. Follow Filtering and Sorting Messages in Outlook article to double-check the settings.
Disable Other Plugins
- Other MAPI or anti-virus plugins may conflict with the Kerio Outlook Connector, resulting in slow load times or message downloads.
- If none of the options above works, it is recommended to temporarily disable any Outlook plugins to identify if there is a conflict causing the degraded performance.
- Make sure to disable Outlook integration with Microsoft Skype for Business as it uses Free/Busy status synchronization.
- If the performance does not improve after disabling the plugin, please contact Kerio support to report the issue.
Folder Synchronization & Limits
- With Outlook 2019, Outlook 2016, Outlook 2013, and Outlook 2010, the maximum number of folders is 500.
- With Kerio Connect, we recommend keeping less than 10,000 items in each folder. If there are folders with over 10,000 items, please split those folders into smaller subfolders.
- NAS is not recommended for storing the KOFF cache. By design, KOFF assumes it is stored in a local disk and based on this executes local Firebird database queries. If NAS is used, the KOFF might experience crashes because the data is corrupted.