On Zimbra OSE (Open Source Edition) version GAL (Global Address List Synchronization) will not synchronize automatically with the local address book of an Outlook. Only on Zimbra desktop can do it with Zimbra OSE version.
Note: On Zimbra Network edition (paid version), it can be synchronize to Outlook with Zimbra LDAP.
Also we have an external plugins (CalDav Synchronizer), through which we can perform GAL sync on Outlook.
1. Download CalDev plugins for outlook through below given link.
2. Now install the plugins on your local outlook of your PC.
3. On Zimbra OSE version we need to manually import the contacts from galsync ID to Contacts folder from Zimbra desktop for one time. Please follow the below given steps.
a. Go to the InternalGAL account and their we can found all contacts.
b. Select the contacts and right click on there. Then press the Move option.
c. You can show the Move Contacts box. Then select the Contacts to move those contacts manually.
4. Now we need to add a synchronization Profile for Contacts.
a. Go to the CalDav Synchronizer tab then press Synchronization Profile.
b. Add a new profile (+ option) and select Generic CalDAV/CardDAV option.
c. Then select OK.
5. Then from outlook need to add below given information on the required field, as shown on above screenshot.
a. Rename the Contacts.
b. Select Outlook folder contacts.
c. Check Synchronize items immediately after changing.
d. Set DEV Url as on screenshot.
e. Now set Username and password on required field. Also check Use IMAP/POP3 account password.
f. Check Test settings and ok.
6. Now it will automatically synchronize the contacts.
7. Now when you will send a mail you can show all email contact's list on To, Cc and Bcc section.
8. If you want to update some more contacts on this list. You need to import those again from zimbra desktop manually for synchronize to your outlook.