MimeKit: How to embed images?

Just for reference, this can be found under http://www.mimekit.net/docs/html/Creating-Messages.htm now. The link in the original answer is broken.

Try something a bit more like this:

var builder = new BodyBuilder ();
var pathImage = Path.Combine (Misc.GetPathOfExecutingAssembly (), "Image.png");
var image = builder.LinkedResources.Add (pathLogoFile);

image.ContentId = MimeUtils.GenerateMessageId ();

builder.HtmlBody = string.Format (@"<p>Hey!</p><img src=""cid:{0}"">", image.ContentId);

message.Body = builder.ToMessageBody ();

If this works for you, I'll update the documentation.

The problem might be that Apple's multipart/related implementation does not resolve the Image.png reference using the Content-Location header on the image mime part (possibly because it is a relative URL).

The cid: URL-type should work, though, but it's a bit more awkward to construct since you need to know the Content-Id values for each image attachment.