Outlook Certificates warning... even when no SSL inspection is enabled

[Pham_Phu_Cuong]

Hi all,

I'm having a proxy policy to allow all to access O365, using all the new ISDB starting with Microsoft in the firmware OS 5.6.4 that I just upgraded to recently, and for this policy I turned off all other functionalities (Webfilter, AV, IPS, AppCntr) and SSL inspection disabled (not even certificate-inspection). This is the only one policy that is there (test environment).

Even then when I use Outlook to access O365 email account, I get certificates warning stating that the certs we're receiving is from Fortigate CA.

Can someone help me explain why? And how can we get rid of this?

One note though, is that all the warnings seem to be related to Autodiscover (have "autodiscover" in the url), and we do have autodiscover turned on in the PCs.

Thanks.

[Pham_Phu_Cuong]

Any ideas anybody?

[Ashik_Sheik]

Hi,

Is it Transparent proxy or explicit proxy policy ?

Regds,

Ashik 

[Pham_Phu_Cuong]

Hi Ashik,

It is explicit proxy policy.

Proxy is deny by default.