The EmbeddedMailObject.Path property specifies the path to the item you want to embed in the mail message constructed declaratively with the System.Web.UI.WebControls.MailDefinition object. The file path in EmbeddedMailObject.Path must be a path such as C:\MyServer\Banner.gif. Typically, the embedded item is an image file. If an image file is referenced by its identifier in the mail message but not included in the message, the image appears as a broken attachment when the e-mail message is viewed.

It is a best practice for accessibility design to set the alternate text property in your mail message for any embedded images.