WFBS can send notifications in the form of email messages to various alerts.
You can configure notifications to apply only to internal email messages by using Custom Internal Email Definitions. This is useful if your company has two or more domains and you would like to treat email messages from both domains as internal email messages. For example, example.com and example.net.
The recipients on your Internal Email Definitions list will receive messages for notifications when you select the Do not notify external recipients check box under the Notification settings for Antivirus, Content Filtering, and Attachment Blocking. Do not confuse the Internal Email Definitions list with the Approved Senders list.
To prevent all email from addresses with external domains from being labeled as spam, add the external email addresses to the Approved Senders lists for Anti-Spam.
The Messaging Security Agent divides email traffic into two network categories: internal and external. The agent queries the Microsoft Exchange server to learn how the internal and external addresses are defined. All internal addresses share a common domain and all external addresses do not belong to that domain.
For example, if the internal domain address is “@trend_1.com”, then the Messaging Security Agent classifies addresses such as “abc@trend_1.com” and “xyz@trend_1.com” as internal addresses. The agent classifies all other addresses, such as “abc@trend_2.com” and “email@example.com” as external.
You can only define one domain as the internal address for the Messaging Security Agent. If you use Microsoft Exchange System Manager to change your primary address on a server, Messaging Security Agent does not recognize the new address as an internal address because Messaging Security Agent cannot detect that the recipient policy has changed.
For example, you have two domain addresses for your company: @example_1.com and @example2.com. You set @example_1.com as the primary address. Messaging Security Agent considers email messages with the primary address to be internal (that is, abc@example_1.com, or xyz@example_1.com are internal). Later, you use Microsoft Exchange System Manager to change the primary address to @example_2.com. This means that Microsoft Exchange now recognizes addresses such as abc@example_2.com and xyz@example_2.com to be internal addresses.