Overview

Mailserver service may occupy full CPU capacity and increase Memory usage, resulting in Kerio Connect server (mailserver.exe process) crashes, segfaults, high CPU, and RAM load. As an outcome, System Health shows all resources being busy and the server's intermittent stops and errors.

Even with low mail traffic, Kerio Connect may face corrupted Fulltext database issues or delayed sync and slow send/receive emails' processing. Problems might be caused by the last update (OS or Kerio Connect software).

Prerequisites

Admin access to Kerio Connect server

Diagnosis

Due to various factors, the Kerio Connect process may experience intermittent issues. The most common reasons are:

• OS or hardware,
• large Calendar .eml files,
• improper setup of macOS EWS account,
• high Open Folder Reference count,
• database (.journal.db), or index (index.fld) corruption.

The mailserver process is consuming all the server resources in order to attempt to fix all of the above issues. It may cause CPU, RAM bottleneck, that may result in a System crash.

Solution

1. As general best-practice, we recommend keeping your OS up-to-date and fully patched. This way all Security requirements are met. It is also advisable to perform regular reboots once each 3-6 months, depending on the server stability. Other specific OS considerations:
   1. Windows: review Event Viewer logs for more information about System Errors and Crashes
   2. Linux: decide which process should be stopped. For more information, please review the Linux OOM Killer article.
   3. macOS: see real-time CPU, network, disk statuses in the Activity Monitor.
2. Several reports received about EWS account in macOS causing high CPU usage. It's recommended to re-configure the accounts and check the Folder Items limits (10.000 maximum).
3. Large Calendar .eml files (over 100 MB) with attachment inside it. It's recommended to review the Calendar folders for particular users (they also might have high Reference Folder). Then remove the identified .eml files or move them to another folder. For Linux/macOS, you can use standard ls -lSh command to sort the files by size:
   
   For Windows, you can sort the files by size by clicking on Size column:
   
4. User Folder corruption that caused High Open Reference Folder count. For more information, please refer to Slow Folder Performance issues.
5. Internal .journal.db and  properties.fld clean-up. Older obsolete properties files, which are no longer used, that may slow down the system. You can use standard Windows del or Linux/macOS rm commands to remove these files altogether:
   
   1. Find the files:
      dir "C:\Program Files\Kerio\MailServer\store\mail\properties.*" /s
   2. If there are any files found, consider running the below delete command:
      Note: The Kerio Connect engine should be stopped before the deletion.
      del "C:\Program Files\Kerio\MailServer\store\mail\properties.fld" /s
      
   3. Similar find and fix procedure can be executed for .journal.db files:
      dir "C:\Program Files\Kerio\MailServer\store\mail\*journal.db" /s
del "C:\Program Files\Kerio\MailServer\store\mail\*journal.db" /s

Confirmation

The system performance is back to normal.