Mailgun Send Send HTML Email with Attachments and HTML Images

Sends an HTML email with images and attachments.
Chilkat C# Downloads

bool success = false;

// This example assumes the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

Chilkat.Http http = new Chilkat.Http();

http.Login = "api";
http.Password = "sending_api_key";//  Replace with your actual sending API key.

Chilkat.HttpRequest req = new Chilkat.HttpRequest();
req.HttpVerb = "POST";
req.Path = "/v3/YOUR_DOMAIN_NAME/messages";
req.ContentType = "multipart/form-data";

// Change YOUR_DOMAIN_NAME to something like "mg.your-domain.com".
req.AddParam("from","Your Name <mailgun@YOUR_DOMAIN_NAME>");
req.AddParam("to","Joe Example <joe@example.com>");
req.AddParam("subject","Hello Joe Example");
req.AddParam("html","<html><body><b>This is the HTML body</b><br><img src=\"cid:cidStarfish.jpg\"></body></html>");

// An a attachd file
Chilkat.BinData bd = new Chilkat.BinData();
success = bd.LoadFile("qa_data/hamlet.zip");
if (success == false) {
    Debug.WriteLine("Failed to load file attachment.");
    return;
}

req.AddBdForUpload("attachment","hamlet.zip",bd,"application/zip");

// add an image as CID
success = bd.LoadFile("qa_data/jpg/starfish.jpg");
if (success == false) {
    Debug.WriteLine("Failed to load HTML image.");
    return;
}

req.AddBdForUpload("inline","cidStarfish.jpg",bd,"image/jpeg");

Chilkat.HttpResponse resp = new Chilkat.HttpResponse();
success = http.HttpSReq("api.mailgun.net",443,true,req,resp);
if (success == false) {
    Debug.WriteLine(http.LastErrorText);
    return;
}

Chilkat.StringBuilder sbResponseBody = new Chilkat.StringBuilder();
resp.GetBodySb(sbResponseBody);
Chilkat.JsonObject jResp = new Chilkat.JsonObject();
jResp.LoadSb(sbResponseBody);
jResp.EmitCompact = false;

Debug.WriteLine("Response Body:");
Debug.WriteLine(jResp.Emit());

int respStatusCode = resp.StatusCode;
Debug.WriteLine("Response Status Code = " + Convert.ToString(respStatusCode));
if (respStatusCode >= 400) {
    Debug.WriteLine("Response Header:");
    Debug.WriteLine(resp.Header);
    Debug.WriteLine("Failed.");
    return;
}

// Sample JSON response:
// (Sample code for parsing the JSON response is shown below)

// {
//   "id": "<20210429234809.1.2D550E1C94D3D98F@sandbox0e542e4c577f4bbb98c8bf6b6bca727b.mailgun.org>",
//   "message": "Queued. Thank you."
// }

// Sample code for parsing the JSON response...
// Use the following online tool to generate parsing code from sample JSON:
// Generate Parsing Code from JSON

string id = jResp.StringOf("id");
string message = jResp.StringOf("message");