email route via new exchange 2013 server

HI guys, 

We have 2 Exchange 2013 Servers. CAS and Mailbox. We have enabled the "Proxy Through Client Access Server" on Send connector. 

we have installed new Exchange 2013 Multi-Role server in the same exchange Organization. After that some external emails trying to relay via new exchange 2013 Server even we did not add that server in to Source Servers on send connector. 

any idea ?