VB.NET
Mailgun Send Send HTML Email with Attachments and HTML Images

Sends an HTML email with images and attachments.
Chilkat VB.NET Downloads

VB.NET
Dim success As Boolean = False

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

Dim http As New Chilkat.Http

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

Dim req As 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
Dim bd As New Chilkat.BinData
success = bd.LoadFile("qa_data/hamlet.zip")
If (success = False) Then
    Debug.WriteLine("Failed to load file attachment.")
    Exit Sub
End If

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

' add an image as CID
success = bd.LoadFile("qa_data/jpg/starfish.jpg")
If (success = False) Then
    Debug.WriteLine("Failed to load HTML image.")
    Exit Sub
End If

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

Dim resp As New Chilkat.HttpResponse
success = http.HttpSReq("api.mailgun.net",443,True,req,resp)
If (success = False) Then
    Debug.WriteLine(http.LastErrorText)
    Exit Sub
End If


Dim sbResponseBody As New Chilkat.StringBuilder
resp.GetBodySb(sbResponseBody)
Dim jResp As New Chilkat.JsonObject
jResp.LoadSb(sbResponseBody)
jResp.EmitCompact = False

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

Dim respStatusCode As Integer = resp.StatusCode
Debug.WriteLine("Response Status Code = " & respStatusCode)
If (respStatusCode >= 400) Then
    Debug.WriteLine("Response Header:")
    Debug.WriteLine(resp.Header)
    Debug.WriteLine("Failed.")
    Exit Sub
End If


' 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

Dim id As String = jResp.StringOf("id")
Dim message As String = jResp.StringOf("message")