This method is a widely used method to migrate email service. You can use it on Zimbra too. Let's take a look at how it works?
Hello.
If it is useful, with imapsync, I use the --authuser option. In the middle of migration of thousands of users, I preffer use the admin password in host1 and host2 this way:
SCRIPT_INI
#!/usr//bin/bash
host1= # host1 IP is Source
host2= # host2 IP is Dest
admin1="adminuser1@dominio1.com"
admin2="adminuser2.dominio2.com"
admpass1="PASSadminuser1"
admpass2="PASSadminuser2"
time imapsync --syncinternaldates
--host1 $host1 --user1 "someuser1@dominio1.com" --authuser1 "$admin1" --password1 "$admpass1" --ssl1
--host2 $host2 --user2 "someuser1@dominio2.com" --authuser2 "$admin2" --password2 "$admpass2" --ssl2
SCRIPT_END
I hope to help. Regards.
@jaimeco Absolutely yes, this is the best solution to migrate from server A to B but it works only if you can use an admin user with delegate access ( not all imap server allow you to use delegate access method ).
Why not move the data and update zimbra version? It's a dns problem, logs say can't resolve imap server.