Windows 10 Outlook will not coect over VPN

Been seeing this issue, hope someone else has solved. When my windows 10 users are coected to VPN, outlook will not coect. No errors, just tries to coect and goes to discoected. Network drives work properly, hostnames resolve, just Outlook not coecting.

When not coected to VPN, Outlook coects fine. However then users do not have network shares etc.

Have not seen this on any Win7 or 8 users.

Details - Windows 10, Office 2013, Watchguard VPN, Exchange 2010.