Zco partial sync

ZCO Partial Account Sync

   KB 24270        Last updated on 2021-03-5  

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ZCO now supports partial account sync that allows users with large accounts the ability to sync a defined number of days worth of messages, Tasks, and calendars to prevent the profile from running into known performance and profile size limitations.

Why was Partial Sync added?

Partial account sync was added because within today’s business environment, it's common for power users to have large mail accounts that can cause Outlook performance issues due to profile size, Outlook version, hardware configuration, and system load. Also, many profiles can now exceed the pst 50 GB file size limit. With Zimbra Connector providing partial sync within Outlook, this allows users to access their most recent data within the Outlook client but still provides the user the ability to store and obtain older data from the Zimbra Web client.

How do you implement Partial Sync?

There are two ways to implement ZCO partial sync, create a new profile or enable within an existing profile. The following is an outline of how to configure, enable, and how ZCO partial sync works.

New profiles

In a default installation, ZCO partial sync is set to disable and the full account will be synced. It is recommended to create a ZmCustomizeMsi.js file to enable and configure an initial sync limit. This will prevent the excessive load and actions of the full account syncing, then having the retention setting purge the unwanted data. The user or admin can also enable these attributes within the registry at:

Computer\HKEY USER\SOFTWARE\Zimbra\CalCutoffDays < N > DWORD
Computer\HKEY USER\SOFTWARE\Zimbra\MsgCutoffDays < N > DWORD

Where <N> is the last number of days that will be synced, the default setting is 0.

Please note, this setting is configured during the initial sync of the account. If the configuration isn't set correctly and the initial sync is started, the profile will need to be recreated to recognize the new initial sync requirements. This method can also be used to set the value without editing the registry. This is because the initial sync and partial sync configuration uses the same registry attributes and is a global configuration. If the user creates a profile using the steps below within the existing profile then purge and creates a new profile, the new profile will inherit the new initial sync attributes.

For steps on how to create a ZCO customized installer, please see the Customizing the Installer section within the Zimbra Connector for Microsoft Outlook: Admin Guide.

Existing profiles

For existing profiles, users can enable the feature by logging into the profile within Outlook, select the Zimbra Ribbon, Advanced option then modify the Synchronization Options settings. There are two options:

  • Purge Calendar Items Older than: Removes all appointments older than configured date.
  • Purge Mail and Task Items older than: Removes all messages and tasks older than the configured date.


Understanding and Managing Partial Sync

When messages are removed from the profile, they are not automatically deleted. The Partial Sync process will move targeted data to a subfolder within trash called Zimbra Trash. This is how the system identifies which data needs to be purged at the server-side vs the client only. Data will stay within the Zimbra Trash folder until the user initiates a Start Purge or Outlook deletes the Zimbra Trash folder from Trash. If the Zimbra Trash folder is deleted, the folder will be recreated during the next retention run.

Users can initiate the purge by selecting Start Purge within the purge section of the Zimbra ribbon.


During a purge, the Start Purge button will show as Pause Purge which will stop the purge at its current status.


Calendaring: All Calendars excluding active reoccurring appointments will be purged outside of the configured purge window. Active reoccurring and all modified instances of an appointment will reside in the calendar until the end date of the reoccurring appointment surpasses the purge date. Increased profile size can be caused by reoccurring appointments where an organizer is modifying instances of a reoccurring appointment with no end date and the appointment has been in existence for years. For reoccurring appointments that do not have an end date and occur daily or weekly, Zimbra recommends setting a defined end date that represents your business cycle, like yearly. Then create a new reoccurring appointment for the next business cycle.

Disable Purge; A User can disable purge by selecting Zimbra Ribbon, Advanced then updating Purge Calendar Items Older than and Purge Mail and Task Items older than to 0. This will require a restart of Outlook and once disabled, the Purge button will be grayed out.

Purge Count: To obtain the number of purged items since the last restart of Outlook, hover the mouse over the Start/Pause Purge button. A display will appear with total items purged since the last restart.


"Idle Profiles:" When accounts are inactive for an extended period of time like due to vacations, at the initial restart, the profiles will sync new data that occurred during the idle time. If the idle days exceed the retention days, new messages could be moved to the Zimbra Trash folder. If the user does not want this to occur, then they need to change the sync day value to 0 or a number of days greater than new messages or pause the purge. Also if the profile is idle for an extended time, the user could get a warning message to rebuild the profile.

ZCO partial sync does not remove the data from the server, only the local profile. Once the message is purge from the local profile, the user can view the message within the Zimbra web client. There is no method to resync purge data.

ZCO partial sync only applies to primary account data. Mounted data from shared profiles or local profiles will not be managed by this process and can affect the performance of Outlook.

ZCO partial sync is disabled in a default installation and will need to be enabled by creating a custom installer or updating the registry.

Upgrading ZCO will retain the existing configuration.

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