CkPython
Mailgun Send Send HTML Email with Attachments and HTML Images

Sends an HTML email with images and attachments.
Chilkat CkPython Downloads

CkPython
import sys
import chilkat

success = False

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

http = chilkat.CkHttp()

http.put_Login("api")
http.put_Password("sending_api_key")#  Replace with your actual sending API key.

req = chilkat.CkHttpRequest()
req.put_HttpVerb("POST")
req.put_Path("/v3/YOUR_DOMAIN_NAME/messages")
req.put_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
bd = chilkat.CkBinData()
success = bd.LoadFile("qa_data/hamlet.zip")
if (success == False):
    print("Failed to load file attachment.")
    sys.exit()

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

# add an image as CID
success = bd.LoadFile("qa_data/jpg/starfish.jpg")
if (success == False):
    print("Failed to load HTML image.")
    sys.exit()

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

resp = chilkat.CkHttpResponse()
success = http.HttpSReq("api.mailgun.net",443,True,req,resp)
if (success == False):
    print(http.lastErrorText())
    sys.exit()

sbResponseBody = chilkat.CkStringBuilder()
resp.GetBodySb(sbResponseBody)
jResp = chilkat.CkJsonObject()
jResp.LoadSb(sbResponseBody)
jResp.put_EmitCompact(False)

print("Response Body:")
print(jResp.emit())

respStatusCode = resp.get_StatusCode()
print("Response Status Code = " + str(respStatusCode))
if (respStatusCode >= 400):
    print("Response Header:")
    print(resp.header())
    print("Failed.")
    sys.exit()

# 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

id = jResp.stringOf("id")
message = jResp.stringOf("message")