We have two forests, one has exchange 2003 servers and the new one we are migrating to has exchange 2010. We need email for our one email domain to flow between the exchange 2003 and exchange 2010 servers and vice versa so as users are moved to the new forest - email still works for them. Two way trust is working. I have a send connector setup for internal in the on the exchange 2010 server which is working and email to recepients on exchange 2003 is going through. (Exchange 2010 is set to non authoritative for the email domain).
On exchange 2003 I have an SMTP connector pointing to the exchange 2010 server. Exchange 2003 is set as authoritative for the email domain -but when I send to recipents in the exchange 2010 forest I get: email account does not exist 5.1.1 error. If I change the exchange 2003 to non auth for the email domain, external users get rejected receipient errors 'unable to relay' when sending to the email domain. Can anyone help us to get this working ?
Thanks in advance