Incoming mail settings in SharePoint 2010 with Exchange online (O365)

I have a SharePoint 2010 farm on premise and there is no exchange or mail system available on premise. I have O365 clients and Exchange online which used to functioning as our company mailing system.

I'm able to configure outbound mail from on premise SharePoint 2010 which works perfectly. My question is, how do I enable "Inbound Mail" to my on premise SharePoint 2010 farm.

Since I'm working for Microsoft vendor, I have a client who required this to enable for Nintex workflow "Lazy Approval" to work. Also I've gone through most forums and didn't found a work arround.

My limitations are, my client doesn't have Public IP neither Exchange server on premise.

Appriciat your quick response

Regards

Shamin

Mohamed Shamin