Forum Discussion
Exchange Hybrid Using 3rd Part Spam Filter
Has anyone ran into an issue using a 3rd part filter in Hybrid Mode? We want the Hybrid connectors to route mail to on prem and office 365. The inbound to Office 365 connector routes correctly. But outbound is failing from Office 365 to On Prem.
- What is the error? You need to allow port 25 (SMTP) connections from the EXO IP addresses to your on-premises Exchange servers for this to work. In my experience, when this fails it's always because the network configuration is blocking this at some point. More details can be found here: https://learn.microsoft.com/en-us/exchange/hybrid-deployment-prerequisites#hybrid-deployment-protocols-ports-and-endpoints
