Ruby
Mailgun Send Send HTML Email with Attachments and HTML Images

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

Ruby
require 'chilkat'

success = false

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

http = Chilkat::CkHttp.new()

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

req = Chilkat::CkHttpRequest.new()
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.new()
success = bd.LoadFile("qa_data/hamlet.zip")
if (success == false)
    print "Failed to load file attachment." + "\n";
    exit
end

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." + "\n";
    exit
end

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

resp = Chilkat::CkHttpResponse.new()
success = http.HttpSReq("api.mailgun.net",443,true,req,resp)
if (success == false)
    print http.lastErrorText() + "\n";
    exit
end

sbResponseBody = Chilkat::CkStringBuilder.new()
resp.GetBodySb(sbResponseBody)
jResp = Chilkat::CkJsonObject.new()
jResp.LoadSb(sbResponseBody)
jResp.put_EmitCompact(false)

print "Response Body:" + "\n";
print jResp.emit() + "\n";

respStatusCode = resp.get_StatusCode()
print "Response Status Code = " + respStatusCode.to_s() + "\n";
if (respStatusCode >= 400)
    print "Response Header:" + "\n";
    print resp.header() + "\n";
    print "Failed." + "\n";
    exit
end

# 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")