Hi Marcmac,
Thanks for pointing to the admin sticky post.
However after reading thru the sticky post, I can't help but feel that it seems unduly complex and still don't know where to configure zimbra such that:
the
user1@example.com on zimbra server to be able to send mails to
user2@example.com that is on a non-zimbra mail server. Instead of getting a bounce that the user does not exist.