An encrypted connection to your mail server is not available

[ahafiz]

Hi,

We're using O365 and I'm not sure if firewall that make thing like this or i need to make some adjustment on O365.

The things is like when I'm trying to connect through exchange server is says "An encrypted connection to your mail server is not available." This is when I'm using firewall (dns). 

But when I used my ISP dns (1.9.1.9) on user computer, it work fine.

Any idea what went wrong ? I'm still new to FortiGate.