TMG doest not support jet Exchange 2013. But with minor changes you get it working 
Change in the OWA Rule
In Exchange 2013 changed the published server logoff URL to /owa/logoff.owa
You need create a Extra Rule Exchange 2013 APPS Rule
You need the ExchangeGuid
Powershell:
Get-Mailbox -Arbitration | where {$_.PersistedCapabilities -like “OrganizationCapabilityClientExtensions”} | fl exchangeGUID, primarysmtpaddress
ExchangeGuid : 3eccca51-d996-49df-b6e0-302d644fdcaa
Totally: