if I understand you correctly, you have enabled sender authentication on your Exchange server for all incomming messages? In this case, you need to configure autgoing authentication on the ESA with a username and password for the Exchange server. The setting can be found under:
GUI: Network->SMTP Authentication
Choose to add a new profile, and make it "Outgoing", then provide the username and password the Exchange server was set up to accept incoming messages. Once submitted, also create an SMTP route for that Exchange server, where you specify the outgoing authentication profile. The user guide has a nice step by step tutorial for that, check the online help of the appliance for "Configuring AsyncOS for SMTP Authentication"
BenefitsDocumentationPrerequisiteImage Download LinksLimitationsSupported PlatformsLicense RequirementsTopologyStep-By-Step ConfigurationConfigure Virtual ServiceActivate the virtual service and configure guest IPsConfiguring UTD (Service Plane)Configurin...
Login to the FXOS chassis manager.
Direct your browser to https://hostname/, and log-in using the user-name and password.
Go to Help > About and check the current version:
Check the current version availa...
We have configured the outside and inside Interface with official ipv6 adresses, set a default route on outside Interface to our router, we also have definied a rule , which also gets hits, to permit tcp from inside Interface to any6.
In Syslog I also se...