Add Second IP receive connector for Internal Relay

Hi All,

I create internal relay for internal scanner to email device , but i found this relay IP will also doing send mail to external user for internal mail to external domain. 

192.168.1.10 (Internet connector)

192.168.1.11 (internal relay connector) 

Sometime it will use 192.168.1.10 to out or sometime it is use 192.168.1.11 to send mail to external.

sometime it willl send to 192.168.1.10 and pass to 192.168.1.11 to out.

Please advise is it normal behavior? 

Thanks.,