Zig
Mailgun Send Email using MIME

Send an email using MIME. This allows for the Chilkat email object to be used to construct the email. Then it can be sent using Mailgun.
Chilkat Zig Downloads

Download Chilkat for Zig
Zig
const std = @import("std");
const chilkat = @import("chilkat");

pub fn main(init: std.process.Init) !void {
    const alloc = init.arena.allocator();

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

    // We're going to create an email that contains an .zip attachment,
    // and also both plain-text and HTML alternative bodies.
    // The HTML body will include an image.

    const email = try chilkat.Email.init();
    defer email.deinit();

    // Adding attachments, HTML/plain-text bodies, etc can be done
    // in any order:

    // Add an attachment
    _ = email.addFileAttachment(alloc, "qa_data/hamlet.zip") catch {
        std.debug.print("{s}\n", .{try email.getLastErrorText(alloc)});
        return;
    };

    // Add some headers:
    email.setSubject("This is a complex email");
    // Please change this email address before testing.
    try email.addTo("Joe Example", "joe@example.com");
    email.setFrom("Your Name <mailgun@YOUR_DOMAIN_NAME>");

    // Add a plain-text body:
    email.addPlainTextAlternativeBody("This is the plain-text body") catch {};

    // Add an image that will be embedded in the HTML body.
    email.addRelatedFile2("qa_data/jpg/starfish.jpg", "starfish.jpg") catch {
        std.debug.print("{s}\n", .{try email.getLastErrorText(alloc)});
        return;
    };

    // Add an HTML body:
    const html = "<html><body><b>This is the HTML body</b><br><img src=\"starfish.jpg\"></body></html>";

    email.addHtmlAlternativeBody(html) catch {};

    // ------------------------------------------------------------------------
    // Send the above email using Mailgun

    const http = try chilkat.Http.init();
    defer http.deinit();

    // Implements the following CURL command:

    http.setLogin("api");
    http.setPassword("sending_api_key"); // Replace with your actual sending API key.

    const req = try chilkat.HttpRequest.init();
    defer req.deinit();
    req.setHttpVerb("POST");
    req.setPath("/v3/YOUR_DOMAIN_NAME/messages.mime");
    req.setContentType("multipart/form-data");

    req.addParam("from", "Your Name <mailgun@YOUR_DOMAIN_NAME>");
    req.addParam("to", "Joe Example <joe@example.com>");
    req.addStringForUpload2("message", "message.eml", try email.getMime(alloc), "utf-8", "application/octet-stream") catch {};

    const resp = try chilkat.HttpResponse.init();
    defer resp.deinit();
    http.httpSReq("api.mailgun.net", 443, true, req, resp) catch {
        std.debug.print("{s}\n", .{try http.getLastErrorText(alloc)});
        return;
    };

    const sb_response_body = try chilkat.StringBuilder.init();
    defer sb_response_body.deinit();
    resp.getBodySb(sb_response_body) catch {};
    const j_resp = try chilkat.JsonObject.init();
    defer j_resp.deinit();
    j_resp.loadSb(sb_response_body) catch {};
    j_resp.setEmitCompact(false);

    std.debug.print("Response Body:\n", .{});
    std.debug.print("{s}\n", .{try j_resp.emit(alloc)});

    const resp_status_code = resp.getStatusCode();
    std.debug.print("Response Status Code = {d}\n", .{resp_status_code});
    if (resp_status_code >= 400) {
        std.debug.print("Response Header:\n", .{});
        std.debug.print("{s}\n", .{try resp.getHeader(alloc)});
        std.debug.print("Failed.\n", .{});
        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

    _ = try j_resp.stringOf(alloc, "id");
    _ = try j_resp.stringOf(alloc, "message");
}