It's necessary configure router/firewall?

[squonk]

I'm connected to the web by a modem/router/firewall (it's a Netgear DG834GT).
When I've installed Zimbra desktop on my laptop I've seen that Zimbra use the 7633 port.
After installation is completed and the account is configurated, Zimbra starts to synchronize the account, but this operation is very slow and is interrupted after some time even if synchronization is finished.
I ask if I must to open the specific port on the firewall to improve the synchronization time.
There is other ports to open on the firewall to make Zimbra works better?
Many thanks!

[phoenix]

You don't need to open any ports on your firewall, the only ports ZD uses are outbound.