Email to Salesforce Services are not fully supported in Salesforce Government Cloud Plus - Defense orgs using .mil framework.
Salesforce automatically creates a unique email address for Email Services including Email-to-Salesforce, Email-to-Case, and Custom Email Services using Apex. When the unique email service address is generated for these features it is created with a .com domain by default.
For example, if this is the service address automatically created by Salesforce:
Then update the .com to .mil and use this email service address instead:
Although the Salesforce generated email service address will still show as .com in Salesforce setup, use the manually updated .mil email variation for your desired implementation.
For example when using Email-to-Case (E2C) in a Government Cloud Plus - Defense Salesforce org, the inbox or "Email Address" that is forwarding to the "Email Service Address" in E2C setup must be a .mil address located within NIPRNet.
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