Exchange 2013 Receiving Internet mail Issue

Hi,,

I am able to send mail to Internet,But i am unable to receive ,My local domain name is intra.mydomain.com

But my external domain name is mydomain.com.I enabled the MX record to mydomain.com and In My firewall router Port 25 forward to the exchange server.Still I am unable to receiving mail.

I tried the receiving connector.But something I missed.

Anyone help me what I missed here?

Thanks.