Whenever a zimbra user send an email from zimbra webmail to any of receipent their sent contact save in Emailed Contacts. So you can import and export the list from from command line .
Run command to get email contact list
$ zmmailbox -z -m shahzad@linuxsolution.in getRestURL “/Emailed Contacts?fmt=csv”
Backup the output in files
$ zmmailbox -z -m shahzad@linuxsolution.in getRestURL “/Emailed Contacts?fmt=csv” > /tmp/emailcontact.csv
Import the backup contact in Zimbra account
zmmailbox -z -m shahzad@linuxsolution.in postRestURL “/Emailed Contacts” /tmp/emailcontact.csv
