Can't access physical host of e-mail server VM after putting FortiMail in network

Recently I implemented a FortiMail VM in transparent mode, SMTP traffic is processed correctly but after putting FortiMail VM in the network i cant access physical host of e-mail server. E-mail server is created as a LXC container in a physical server with Ubuntu 16.04.

I tested the same scenario using VMware Esxi and everything is working fine.

I am confused for the first scenario, why the traffic is blocked. before putting FortiMail in network   I can access the physical host of e-mail server. FortiMail in transparent mode act as a layer 2 switch (no routes are created)