The Retain Worker is the component that pulls the data from the messaging source, whether that be an email system or a mobile device.
48080 (TCP) Requires outgoing access if on a server external to the Retain Server.
80 or 443 (TCP HTTP or HTTPS) Requires incoming access to reach the Worker web interface
Other ports must be opened on the server hosting the Retain Worker, depending on the modules being used; and, in some cases, on servers hosting the messaging system Retain is archiving.