(Node.js) Send HTML Email with CSS as Related Item using Content-Location

Demonstrates how to compose an HTML email with an external CSS file included as a related item and referenced by Content-Location.

Some email clients display embedded (related) content best using CID's (Content-IDs), whereas other email clients display related content best by Content-Location. The choice you make may depend on the software used by the intended recipient of your email. (Does' the recipient read email on an iPhone? Android? Outlook? GMail? Thunderbird? etc.)

Install Chilkat for Node.js and Electron using npm at

Chilkat npm packages for Node.js
Chilkat npm packages for Electron
on Windows, Linux, MacOSX, and ARM

var os = require('os');
if (os.platform() == 'win32') {  
    if (os.arch() == 'ia32') {
        var chilkat = require('@chilkat/ck-node21-win-ia32');
    } else {
        var chilkat = require('@chilkat/ck-node21-win64'); 
    }
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node21-arm');
    } else if (os.arch() == 'x86') {
        var chilkat = require('@chilkat/ck-node21-linux32');
    } else {
        var chilkat = require('@chilkat/ck-node21-linux64');
    }
} else if (os.platform() == 'darwin') {
    if (os.arch() == 'arm64') {
        var chilkat = require('@chilkat/ck-node21-mac-m1');
    } else {
        var chilkat = require('@chilkat/ck-node21-macosx');
    }
}

function chilkatExample() {

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

    // The mailman object is used for sending and receiving email.
    var mailman = new chilkat.MailMan();

    // Use your SMTP server hostname.  This example uses office365, but it could be any SMTP server..
    mailman.SmtpHost = "outlook.office365.com";
    mailman.SmtpPort = 587;
    mailman.StartTLS = true;

    // Set the SMTP login/password
    mailman.SmtpUsername = "OFFICE365-SMTP-LOGIN";
    mailman.SmtpPassword = "OFFICE365-SMTP-PASSWORD";

    // Create a new email object
    var email = new chilkat.Email();
    email.Subject = "HTML Email with embedded CSS";
    email.From = "Chilkat Support <my-office365-user@mydomain.com>";
    email.AddTo("Chilkat Support","support@chilkatsoft.com");

    var sbCss = new chilkat.StringBuilder();
    var bCrlf = true;
    sbCss.AppendLine("body {",bCrlf);
    sbCss.AppendLine("    background-color: powderblue;",bCrlf);
    sbCss.AppendLine("}",bCrlf);
    sbCss.AppendLine("h1 {",bCrlf);
    sbCss.AppendLine("    color: blue;",bCrlf);
    sbCss.AppendLine("}",bCrlf);
    sbCss.AppendLine("p {",bCrlf);
    sbCss.AppendLine("    color: red;",bCrlf);
    sbCss.AppendLine("}",bCrlf);

    // The filenameInHtml is what should exists within the HTML (in the href atribute)
    var filenameInHtml = "styles.css";
    // Call AddRelatedString2 to use Content-Location.
    email.AddRelatedString2(filenameInHtml,sbCss.GetAsString(),"utf-8");

    var sbHtml = new chilkat.StringBuilder();
    sbHtml.AppendLine("<!DOCTYPE html>",bCrlf);
    sbHtml.AppendLine("<html>",bCrlf);
    sbHtml.AppendLine("<head>",bCrlf);
    sbHtml.AppendLine("  <link rel=\"stylesheet\" href=\"styles.css\">",bCrlf);
    sbHtml.AppendLine("</head>",bCrlf);
    sbHtml.AppendLine("<body>",bCrlf);
    sbHtml.AppendLine("",bCrlf);
    sbHtml.AppendLine("<h1>This is a heading</h1>",bCrlf);
    sbHtml.AppendLine("<p>This is a paragraph.</p>",bCrlf);
    sbHtml.AppendLine("",bCrlf);
    sbHtml.AppendLine("</body>",bCrlf);
    sbHtml.AppendLine("</html>",bCrlf);

    email.SetHtmlBody(sbHtml.GetAsString());

    var success = mailman.SendEmail(email);
    if (success !== true) {
        console.log(mailman.LastErrorText);
    }
    else {
        console.log("Mail Sent!");
    }


}

chilkatExample();