Troubleshooting Tip : IMAPS may fail to connect through a FortiGate if CA certificate is not installed - FortiOS 4.0 and above

[dchan]

Description

Problem :

IMAPS fails to connect when a protection profile is enabled.

Explanation :

Whenever the IMAPS proxy is triggered, the FortiGate unit will perform deep inspection for this traffic. Therefore, during the security handshake, the FortiGate unit will send it's local self-signed certificate to IMAPS client.

The connection will fail as IMAPS client does not have a proper certificate installed.

Scope
FortiOS 4.0 and above
Solution

 Import a proper CA signed certificate on the FortiGate unit as well as on IMAPS client.