Hello We have 2 Exchange 2010 servers. I have installed Exchange 2013 server and created mailbox in it. Problem is that user account from Exchange 2013 server cannot sent mail to user in Exchange 2010 mailbox server. Do i need to create any aditional send\receive connectors to be able to do that? It i telnet from exchange 2013 server to exchange 2010 CAS i send email message to exchange 2010 mailbox without any problems.

Yes, I had to create a Receive connector on the Exchange 2010 server, with the IP's of the 2013 servers. With the authentication of Exchange Server.http://jaworskiblog.com