Send HTML Email with External CSS as Related Item

See more SMTP Examples
Demonstrates how to compose an HTML email with an external CSS file included as a related item and referenced by CID (Content-ID).
Chilkat Go Downloads

Download Chilkat for Go
    success := false

    // 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.
    mailman := chilkat.NewMailMan()

    // Use your SMTP server hostname.  This example uses office365, but it could be any SMTP server..
    mailman.SetSmtpHost("outlook.office365.com")
    mailman.SetSmtpPort(587)
    mailman.SetStartTLS(true)

    // Set the SMTP login/password
    mailman.SetSmtpUsername("OFFICE365-SMTP-LOGIN")
    mailman.SetSmtpPassword("OFFICE365-SMTP-PASSWORD")

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

    sbCss := chilkat.NewStringBuilder()
    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)

    // It's possible to add a CSS file directly by calling AddRelatedFile.
    // This example will add the CSS from a string.
    filenameInHtml := "styles.css"
    contentIdCss := email.AddRelatedString(filenameInHtml,*sbCss.GetAsString(),"utf-8")
    if email.LastMethodSuccess() != true {
        fmt.Println(email.LastErrorText())
        mailman.DisposeMailMan()
        email.DisposeEmail()
        sbCss.DisposeStringBuilder()
        return
    }

    // The src attribute for the image tag is set to the contentIdCss:
    sbHtml := chilkat.NewStringBuilder()
    sbHtml.AppendLine("<!DOCTYPE html>",bCrlf)
    sbHtml.AppendLine("<html>",bCrlf)
    sbHtml.AppendLine("<head>",bCrlf)
    sbHtml.AppendLine("  <link rel=\"stylesheet\" href=\"cid:CONTENT_ID_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)

    numReplacements := sbHtml.Replace("CONTENT_ID_CSS",*contentIdCss)

    email.SetHtmlBody(*sbHtml.GetAsString())

    success = mailman.SendEmail(email)
    if success != true {
        fmt.Println(mailman.LastErrorText())
    } else {
        fmt.Println("Mail Sent!")
    }


    mailman.DisposeMailMan()
    email.DisposeEmail()
    sbCss.DisposeStringBuilder()
    sbHtml.DisposeStringBuilder()