Hi Robert,
Thank you for contacting Aspose support team.
You may use alternate views to add plain text and html bodies to display proper body according to the viewer capabilities. Please give a try to the following sample code and share the feedback.
String path = "";
MailMessage SampleMsg = new MailMessage();
SampleMsg.Subject = "Test Email 5.8 with Linked resource in AlternateView";
AlternateView plainView = AlternateView.CreateAlternateViewFromString("This is my plain text content", null, "text/plain");
AlternateView htmlView = AlternateView.CreateAlternateViewFromString("Here is an embedded image.", null, "text/html");
LinkedResource logo = new LinkedResource(path + @"Desert.jpg", MediaTypeNames.Image.Jpeg);
logo.ContentId = "companyLogo";
htmlView.LinkedResources.Add(logo);
SampleMsg.IsBodyHtml = true;
SampleMsg.AlternateViews.Add(plainView);
SampleMsg.AlternateViews.Add(htmlView);
//Set From, To, ReplyToList
SampleMsg.From = new MailAddress("user1@gmail.com");
SampleMsg.To.Add(new MailAddress("user2@gmail.com"));
MailAddressCollection coll = new MailAddressCollection();
coll.Add(new MailAddress("user3@gmail.com"));
//msgReply.ReplyToList = coll;
SmtpClient client = new SmtpClient("smtp.gmail.com", 587, "user1@gmail.com", "password", SecurityOptions.Auto);
client.Send(SampleMsg);