We have several locations running Fortinet equipment and we can't get to our on-prem Exchange server when using WiFi from only one of the locations.
Main office has a Fortigate 200. Outlaying offices both have Fortigate 100E. A site-to-site tunnel connects everything. When we're at the main office and on WiFi, any iPhone will connect to email using the Mail app perfectly. When we go to office A with the same iPhone, everything works fine. When we go to Office B (running FortiOS 6.2.11) with the same iPhone, we can't reach the Exchange server (via mail app or owa address). We're able to ping the server just fine. If we use an Android or a laptop in that same office, there is no issue - it is ONLY the iPhone.
Sniffer logs show the Client Hello going from the iPhone to the Exchange server. Logs on the HQ 200 show that the Server Hello gets sent to the 100E but then the connection times out (maybe due to using TLS 1.0 somehow?).
Again - the same iPhone will work in our other locations just fine. It's only this ONE location that is having issues.
Has anyone experienced something similar? Does anyone know of any magic setting in the 100E that may need to be changed? Is there a way to use the 100E to find out what happens to the traffic?