Sending Email In C# & .NET - Part 9 - Sending Multiple Format Email Using SMTP | Conrad Akunga

This is Part 9 of a series on sending email.

In our last post, Sending Email In C# & .NET - Part 8 - Sending HTML Email Using SMTP, we looked at how to send HTML email via SMTP.

In this post, we will look at how to create an email with multiple formats.

The use case here is that, on paper, HTML seems to be the superior format.

You can format the text (bold, italic, underline).
You can include images inline.
You can embed hyperlinks.
You can use constructs like tables and CSS for advanced styling.
You can embed video.
You can track the opening of the email.

The reality is that HTML email can also cause problems.

Some mail clients do not support HTML email.
Even those that do, they support different subsets of the specification.
Even for those subsets universally supported, there are subtle differences in the rendering
Some people do not want to read HTML email.

To work around this issue, it is advisable always to send a plain text version of your HTML email.

To achieve this, we create two AlternateViews - one for the HTML content and the other for the plain text content.

var mail = new MailMessage();
mail.From = new MailAddress("operations@MI5.co.uk", "M");
mail.To.Add(new MailAddress("jbond@MI5.co.uk", "James Bond"));
mail.Subject = "Happy 50th Birthday James";

// HTML body with image reference to linked resource by ID
const string htmlBody = """
                        <html><body>
                        Good afternoon.
                        <br>
                        Have a happy birthday today!
                        <br>
                        <br>
                        <img src='cid:Image1' />
                        </body></html>
                        """;

// AlternateView for HTML with linked image
var htmlView = AlternateView.CreateAlternateViewFromString(htmlBody, null, MediaTypeNames.Text.Html);

// Load image and link it to the HTML view
var passPortPhoto = new LinkedResource("jamesBond.png", MediaTypeNames.Image.Png)
{
    ContentId = "Image1",
    ContentType = new ContentType(MediaTypeNames.Image.Png),
    TransferEncoding = TransferEncoding.Base64
};

htmlView.LinkedResources.Add(passPortPhoto);
mail.AlternateViews.Add(htmlView);

// Plain text view for non-html friendly situations
const string plainTextBody = """
                             Good afternoon.

                             Have a happy birthday today!


                             """;

var plainTextView = AlternateView.CreateAlternateViewFromString(plainTextBody, null, MediaTypeNames.Text.Plain);
mail.AlternateViews.Add(plainTextView);