SMTP call forward is a form of Mimecast recipient validation. It makes a connection to your organization's Exchange server(s) to determine the validity of a recipient on an inbound email. Before this type of recipient validation can be used for an internal domain:
- Anti-spam features must be installed.
- Exchange recipient filtering must be enabled.
What You'll Need
- Admin permissions to your organization's Exchange environment.
Installing Anti-Spam Features on a Hub Transport Role Server
To enable Exchange recipient filtering, anti-spam features must be installed. The process differs according to the version of Exchange you have. See the relevant link below for full details:
Enabling Recipient Validation
The process to enable Exchange recipient filtering differs according to the version of Exchange you have. See the relevant link below for full details: