We are on ZCS 5.0.14.
We have configured zimbra GAL as follows
GAl lookup Mode 'Both'.
Ldap Filter = (|(cn=%s)(sn=%s)(gn=%s)(uid=%s)(mail=%s))
Autocomplet filter = externalLdapAutoComplete
Ldap Url = ldap://Server1.test.com:389

We are using Domino LDAP.
localconfig settings are as follows,

zimbraGalInternalSearchBase ROOT
zimbraGalSyncInternalSearchBase ROOT

zmprove gac -v command gives the following,

zimbraFeatureGalAutoCompleteEnabled: TRUE
zimbraFeatureGalEnabled: TRUE
zimbraFeatureGalSyncEnabled: TRUE

The issue is GAL lookup (external & internal) happens properly using web client but in Zimbra desktop client (tried two versions 2.0.1 & 7.0) only internal GAL is getting offling synced but not the external.
This is stopping us to let the user get rich expriance of Zimbra Desktop Client. Quick reply would be highly appreciated. thanks in advance.