Is there any way to send HTML e-mail with embedded image in UWP

I am working on a uwp app to send html email with embedded image. I was using EASendMail nuget pakage and it was fine after some time my app shows error:

A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond. (Exception from HRESULT: 0x8007274c)

I think the trial period has expired what should I do?

using EASendMailRT; https://www.emailarchitect.net/easendmail/kb/csharp.aspx?cat=8

I can't find any alternative

try
{
    string ToAddress = MailSendPage.toAddressTxtBox;
    string Subject = MailSendPage.subjectTxtBox;
    SmtpMail oMail = new SmtpMail("TryIt");
    oMail.From = new MailAddress(username);

if(!String.IsNullOrEmpty(ToAddress)&& !String.IsNullOrEmpty(Subject))
{
    oMail.To.Add(new MailAddress(ToAddress));
    oMail.Subject = Subject;
    EASendMailRT.SmtpClient oSmtp = new EASendMailRT.SmtpClient();
    SmtpServer oServer = new SmtpServer(host);
    oServer.User = username;
    oServer.Password = password;
    oServer.Port = port;
    if (IsStackPanalHasImg() == true)
    {
        StorageFolder localFolder = ApplicationData.Current.LocalFolder;
        string[] files = Directory.GetFiles(localFolder.Path + @"\ProjectImages");
        foreach (string eachfile in files)
        {
            foreach (string name in covertToHtml.ControlName)
            {
                string pattern = string.Format("{0}.jpeg", name);
                if (Regex.IsMatch(eachfile, pattern))
                {
                    Attachment oAttachment = await oMail.AddAttachmentAsync(eachfile);
                    oAttachment.ContentID = name;
                }
            }
        }
    }



    await oSmtp.SendMailAsync(oServer, oMail);
    popUpMsgs.popup(" The Mail has been sent");
}

} catch (Exception ep) { popUpMsgs.popup(String.Format("Failed to send email with the following error: {0}", ep.Message)); }

The built-in e-mail API only support sending plain text e-mail messages as Docs state:

This method only sends plain text messages. You can't set the body of the message to the HTML format.

What you can do is attach images to the e-mail:

EmailMessage mail = new EmailMessage();
mail.Sender = new EmailRecipient("test@example.com");
mail.To.Add(new EmailRecipient("someone@example.com"));
mail.Subject = "Hello";
mail.Body = "World";
var file = await StorageFile.GetFileFromApplicationUriAsync(
      new Uri("ms-appx:///Assets/StoreLogo.png"));
mail.Attachments.Add(new EmailAttachment(file.Name, file));
await Windows.ApplicationModel.Email.EmailManager.ShowComposeNewEmailAsync(mail);

In addition, sending attachments works well only in case of the built-in UWP Outlook Mail client. Classic Outlook will most likely ignore the attachments altogether.

If you need to embed the image, you will need to use a e-mail service. I can recommend SendGrid or MailGun. Both have C# APIs which work like a breeze. They are also free for limited number of e-mails.

There are several ways you can embed the images in a HTML e-mail message.

The oldest is using CID (Content ID) which you were using in your question.

Second option is using Base64 encoding. You first turn your image into a Base64 string. There are many tutorials on this, for example in this blogpost. Then you can just embed the image in the src of your <img> tag:

<img src="data:image/jpeg;base64, YOURIMAGEINBASE64"/>

Finally you can embed an image which is hosted somewhere. This scales the best if you need to send the e-mail to many recipients, but of course requires actually hosting the image somewhere. Of the three methods it is also supported in most clients.

All three approaches are described in detail in this post.