(C#) 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.)

Chilkat .NET Downloads

Chilkat .NET Framework

Chilkat for .NET Core

// 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.
Chilkat.MailMan 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
Chilkat.Email 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");

Chilkat.StringBuilder sbCss = new Chilkat.StringBuilder();
bool 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)
string filenameInHtml = "styles.css";
// Call AddRelatedString2 to use Content-Location.
email.AddRelatedString2(filenameInHtml,sbCss.GetAsString(),"utf-8");

Chilkat.StringBuilder 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());

bool success = mailman.SendEmail(email);
if (success != true) {
    Debug.WriteLine(mailman.LastErrorText);
}
else {
    Debug.WriteLine("Mail Sent!");
}