As noted earlier, SQL Server relies on Service Broker (SSB) to activate the Database Mail process (
DatabaseMail.exe) used to send mail.
DatabaseMail.exe uses ADO.NET to connect to SQL Server and to read from and write to SSB queues (found in
msdb) that hold send requests and send statuses in the form of typed SSB messages. You can view these queues (
ExternalMailQueue) in the Object Browser by selecting
Service Broker and then the
Queues folder. If you look a bit further in the Object Browser, you see how the mail transmission architecture is implemented (in part) as an SSB application, as you find the corresponding internal and external Database Mail SSB services (
InternalMailService and ...