I've realized a configuration of postfix that will put in the queue all the emails to send (deferred queue) and, when I want, the email to send will be relayed to the main mailserver.
Now I've 2 questions:
1) How to queue the emails directly in Hold?
I've setup main.cf with this lines:
transport_maps = hold:[mail.domain.com]
defer_transports = hold
default_transport = hold
virtual_transport = hold
hold unix - - n - - smtp
2) How to setup postfix to not queue and relay the internal emails?
All the internal emails will have the same domain (domain.com).
Thanks a lot