1.   Open the ‘exchange management console’ < click the ‘organization configuration’ < select ‘hub transport’.

2. Right click< ‘new send connector’.
3. Give a name to the connector (like: Domain_SPConnector).
4. In address space < click ‘add’ and enter the fully qualified domain name that
    was Configured for the SharePoint server.
5. In ‘network settings’< select ‘route mail through the following smart hosts’
6. Click ‘add’ < enter the smart host IP address or domain name.
7. In ‘Smart Host Authentication’ < accept the default.
8. Make sure the ‘Source Server’ tab marked with your Exchange server.