Zimbra internal and external domains

[doctor_house]

Good day,

I have just installed a zimbra instance on a virtual machine to test it. It works but i fail at understanding a couple of things.
My situation is this
the internal domain is "smtp.network.local" and i have a domain managed with dyndns called 2gnetworks.net .
I set up a couple of accounts giulio@2gnetworks.net and giovanna@2gnetworks.net. Now i fail at understanding if when mr. giulio sends an email to ms giovanna it goes in and out or zimbra performs a check with its internal addresses and simply forwards it internally without really using the internet connection.

thanks for your help and 10+ to this fabulous product

[phoenix]

My situation is this
the internal domain

I assume from that comment that you're behnd a NAT router?

is "smtp.network.local" and i have a domain managed with dyndns called 2gnetworks.net .

Why don't you take the easy route and name your internal domain the same as your external domain, it will save you a lot of confusion.