POP access can be enabled as a global setting or server setting. The server settings overrule the global settings.
Go to Configure>Global Settings.
Click POP in the Navigation pane.
Select Enable POP3 services to allow POP connection to the Zimbra servers.
Select Enable SSL for POP service to enable encrypted connections (HTTPS) or Enable clear text login to enable connects that are not encrypted (HTTP).
Set the number of threads that should be available. The default is 100. The number set here is used for the server configuration of POP.
Click Save.
Restart the server in order to have these changes take effect. (CLI command zmcontrol restart)
Go to Configure>Severs.
Select the server to edit and in the gear icon click Edit.
Click POP in the Navigation pane.
Select Enable POP3 services to allow POP connection to the Zimbra servers.
Select Enable SSL for POP service to enable encrypted connections (HTTPS) or Enable clear text login to enable connects that are not encrypted (HTTP).
Set the advertised name to identify the server when a POP client connects. The default is the local server name.
Set the address as the local IP address the POP service should bind to. This is the interface address on which POP3 servers should listen to. If this is empty, it binds to all interfaces.
Set the POP3 and POP3 SSL port numbers
Click Save.
Restart the server in order to have these changes take effect. (CLI command zmcontrol restart)