ZCO Releases

ZCO Release History

   KB 24388        Last updated on 2021-11-9  

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  • ZCO connectors are backwards compatible. If running a newer ZCO version, you must uninstall it before installing an older version.
  • There may be incompatibilities with older versions of ZCO and newer versions of Outlook.
  • The major build number in the ZCO file name has no bearing on the version. and are the same. The build ID is the last portion of the version. In the table below, it is the first column.
  • Zimbra always recommends using the latest version of the connector when possible. Downgrade at your own risk.
  • In cases where ZCO versions spanned multiple patches, the date listed is the date in which the ZCO version was introduced (the earliest patch).

ZCO Build ID Date (MM/DD/YY) 8.8 Patch 9.0 Patch Known Changes Files
1907 10/25/21 P27 P20 Warning: It has been identified that on some 32 bit systems, the ZCO connector will fail to automatically fetch email without pressing send receive. Until a fix is released, you can use build 1899.
When *zimbraMtaMaxMessageSize* was set to zero, ZCO users were not able to send emails. The issue has been fixed.
When using mixed ZCO profiles (Exchange and Zimbra), sending an email with an attachment resulted in an error. The issue has been fixed.
x64 x86
1903 08/30/21 P26 P25 P19 P18 Affected by 32 bit send/receive bug. 32 bit users use build 1899
Users now have an option to switch between the Zimbra Free Busy and Internet-Free Busy Provider. The option can be accessed at Zimbra -> Advanced Settings -> Free-Busy Providr. Please note that Outlook has to be run as an Administrator to view this option.
x64 x86
1902 07/26/21 P24 P17 Affected by 32 bit send/receive bug. 32 bit users use build 1899
Room finder feature available in ZCO! Users can use Room finder to search rooms based on criteria such as name/capacity and select room(s) as per their availability.
x64 x86
1899 06/03/21 P23 P22 P16 P15 When the emails from the shared account are deleted, the deleted emails were moved to the user's local Trash folder. The issue has been fixed and in such a scenario the emails are moved to the shared account's Trash folder.
If Outlook 2019 has a multi-user profile (Exchange+Zimbra), then sending an email caused Outlook to crash. The issue has been fixed.
x64 x86
1894 04/26/21 P21 P14 ZCO now supports separate controls to configure purging of Mail Items and Tasks. Please refer to the user guide for more details
Through the Hierarchical Address Book dialog, the user can now pick recipients from the lists and proceed to email/meeting compose windows.
x64 x86
1893 03/30/21 P20 P13 When a user has a signature and sends a message using Apple Mail with attachments, the signature is also sent as an attachment and is not a part of the message body. This issue is due to a bug in the Apple Mail client.
x64 x86
1892 02/22/21 P19 P12 A warning message is shown to the user when they change the ZCO Advanced Settings. The user needs to restart Outlook for the changes to take effect.
If network connection was lost when HAB Synchronization is in progress, the synchronization process didn't exit gracefully. The issue has been fixed to handle such situations gracefully.
x64 x86
1891 01/25/21 P18 P11 The Hierarchical Address Book feature is now available in Zimbra's Connector for Outlook. Please refer to the user guide for more details.
The Partial Data Synchronization feature is now available in Zimbra's Connector for Outlook. Please refer to the user guide for more details.
x64 x86
1888 12/16/20 P17 P10 With this release, ZCO has enhanced the address book search feature. The search now includes looking for substrings within the name fields. It is effective specifically when the fields contain multiple words. For more details, please refer to the admin guide section.
x64 x86
1887 11/24/20 P16 P15 P9 P8 ZCOMT-1466 Cannot move/store zdb file to the external location in case of Outlook 2016 and 2019
x64 x86
1886 09/22/20 P14 P7 Users can now synchronize the last X days of Inbox and Calendar data during Initial Sync.
Localization is available for new features like Free-Busy, Run Rule Now, Send the signature picture as attachments.
x64 x86
1884 08/27/20 P13 P6 Custom ZCO installer with "--disable-autoupgrade" option was not working and it continued to ask users to upgrade as soon as the new version was present. The issue has been fixed and it doesn't prompt users to upgrade.
x64 x86
1880 07/27/20 P12 P5 ZCOMT-2074 checkmarx: fix the 'Process Control' reported errors
ZCOMT-2019 "Soap Fault. Permission denied error while forwarding meeting invite from ZCO
ZCOMT-1977 Sync fails if a signature is named with characters not valid for Windows filenames
ZBUG-1209 ZCO SendAs Problems, emails not getting improper sent folder
x64 x86
1879 07/02/20 N/A P4 Fixed an internationalization problem with the mailbox rules "Run Now" feature, that caused an error message if the language was set using a Language Interface pack instead of the language options in the advanced settings.
Signatures containing external images (URL references) had those images added as attachments to messages. Such messages would appear in "has:attachment" searches when the only attachment was the signature image.
Users now have an advanced option, "Signature pictures sent as attachments" to control this behavior. When disabled, the image URL will be used without an additional attachment, thereby reducing the size of the message.


1878 07/02/20 P11 N/A Inline images in meeting notes now sync to Zimbra and are encoded to appear as inline images in the Zimbra Web Apps, instead of being attachments.
**Warning: Using a version below this row can result in a crash or hang due to: (ZCOMT-1978) WAITSET and/or SYNCMAIN Deadlock**
1877 06/03/20 P10 N/A ZCOMT-1803 Inconsistent font size rendering issue on Rules wizard
1876 06/03/20 N/A P3 Zimbra Free/Busy Provider is now Generally Available. Refer to the Admin Guide for operation details.
When creating a new Rule (aka Zimbra Filter) using ZCO, the user is given the option to run it immediately.
x64 x86
1872 04/22/20 P9 P2 Duplicate calendar events would sometimes appear, with no clear trigger action. ZCO now identifies these unwanted duplicates and automatically removes them.
Fixed several possible crashes that would occur periodically when modifying events in shared or delegated calendars.
1869 04/17/20 N/A GA None in release notes x64 x86
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