Mail and calendar synchronization via ActiveSync between Plesk server with Premium Email (Kolab) and mail client does not work: Uncaught Error: Class 'kolab_auth' not found

Symptoms

• Mail and calendar synchronization via ActiveSync between a Plesk server with Premium Email (Kolab) and a mail client does not work.

• The following error messages are found in the log files /var/log/maillog or /var/log/kolab-syncroton/errors.log:

  CONFIG_TEXT: IMAP Error: Login failed for john_doe@example.com against localhost from 127.0.0.1(X-Real-IP: 203.0.113.2,X-Forwarded-For: 203.0.113.2). Authentication failed. in /usr/share/roundcubemail/program/lib/Roundcube/rcube_imap.php on line 201 (OPTIONS /Microsoft-Server-ActiveSync) [08-Jan-2019 21:30:09 Europe/London] PHP Fatal error: Uncaught Error: Class 'kolab_auth' not found in /usr/share/kolab-syncroton/lib/kolab_sync.php:235 Stack trace:
  ..........

  ---

  CONFIG_TEXT: PHP Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 56371791 bytes) in /usr/share/kolab-syncroton/lib/ext/Syncroton/Model/AXMLEntry.php on line 199

Cause

The maximum amount of memory that the script is allowed to allocate is not enough to perform the synchronization task.

Resolution

1. Connect to the server using SSH.

2. Find the file php.ini used by the webmail for the domain example.com:

   • On CentOS/RHEL:

     # grep PHP_INI /etc/httpd/conf/plesk.conf.d/webmails/example.com_webmail.conf
     FcgidInitialEnv PP_CUSTOM_PHP_INI "/etc/php.ini"

   • On Debian or Ubuntu:

     # grep PHP_INI /etc/apache2/plesk.conf.d/webmails/example.com_webmail.conf
     FcgidInitialEnv PP_CUSTOM_PHP_INI "/etc/php/7.0/apache2/php.ini"

3. Open the file found on step 2 with a text editor, e.g. vi.

4. Increase the value of the parameter memory_limit and save the file:

   CONFIG_TEXT: memory_limit = 128M

5. Restart Apache to apply changes:

   • On CentOS/RHEL:

     # service httpd restart

   • On Debian or Ubuntu:

     # service apache2 restart