[C#]
// Standard CRM Service Setup
CrmService service = new CrmService();
service.Credentials = System.Net.CredentialCache.DefaultCredentials;

CrmService service = new CrmService();
service.Credentials =
    System.Net.CredentialCache.DefaultCredentials;

// Get the ID of the system user.
WhoAmIRequest userRequest = new WhoAmIRequest();
WhoAmIResponse user = 
    (WhoAmIResponse) service.Execute(userRequest);

// Specify the system user who is sending the message.
service.CallerIdValue = new CallerId();
service.CallerIdValue.CallerGuid = user.UserId;

// Create a SendEmail request.
SendEmailRequest req = new SendEmailRequest();
req.EmailId = new Guid("A0F2D8FE-6468-DA11-B748-000D9DD8CDAC");
req.TrackingToken = "";
req.IssueSend = true;

// Send the email message.
SendEmailResponse res = (SendEmailResponse)service.Execute(req);

[Visual Basic .NET]
' Standard CRM Service Setup
Dim service As New CrmService()
service.Credentials = System.Net.CredentialCache.DefaultCredentials

' Get the ID of the system user.
Dim userRequest As WhoAmIRequest = New WhoAmIRequest
Dim user As WhoAmIResponse = 
    CType(service.Execute(userRequest), WhoAmIResponse)

' Specify the system user who is sending the message.
service.CallerIdValue = New CallerId
service.CallerIdValue.CallerGuid = user.UserId

' Create a SendEmail request.
Dim req As SendEmailRequest = New SendEmailRequest
req.EmailId = New Guid("A0F2D8FE-6468-DA11-B748-000D9DD8CDAC")
req.TrackingToken = ""
req.IssueSend = True

' Send the email message.
Dim res As SendEmailResponse = 
    CType(service.Execute(req), SendEmailResponse)