Unable to send embedded images with Azure Communication Service SMTP

Aalap 0

I'm unable to send an email with embedded images with ACS SMTP. The same code works for other non-ACS SMTP servers. I'm creating an alternate view and a linked resource with matching ContentID.
User's image

public void SendEmail()
		{
			MailMessage mail = new MailMessage
			{
				From = new MailAddress(_sender),

				Subject = "Test Email with embedded image",

				IsBodyHtml = true
			};

			mail.To.Add(_recipient);

			string htmlBody = "<html><body><p>This is an email with an embedded image.</p><img src='cid:image001'></body></html>";

			AlternateView htmlView = AlternateView.CreateAlternateViewFromString(htmlBody, null, MediaTypeNames.Text.Html);
			using (FileStream imageStream = new FileStream(@"D:\Pictures\logo.jpg", FileMode.Open, FileAccess.Read))
			{
				LinkedResource inlineImage = new LinkedResource(imageStream, "image/jpeg") { ContentId = "image001" };
				htmlView.LinkedResources.Add(inlineImage);
				mail.AlternateViews.Add(htmlView);
				SmtpClient smtpClient = new SmtpClient(_smtpHost)
				{
					Credentials = new NetworkCredential(_smtpUsername, _smtpPassword),
					Port = 587,
					EnableSsl = true
				};

				try
				{
					smtpClient.Send(mail);
					Console.Write("Email sent successfully!");
				}
				catch (Exception ex)
				{
					Console.Write("Error sending email: " + ex.Message);
				}
			}
		}

Laxman Reddy Revuri 2,945 Reputation points Microsoft External Staff

2025-03-07T06:54:04.2733333+00:00

Hi @Aalap
Try sending the email with a different image format (e.g., PNG instead of JPG) to rule out format-specific issues. Smaller images are less likely to be blocked by SMTP. The ContentId in LinkedResource must match cid:image001 in the email body. ACS provides email logs via Azure Monitor. Check the logs to see if ACS is stripping out the inline image:

Go to Azure Portal → Azure Communication Services.

Navigate to Diagnostics Settings.

Enable logging and check for possible errors.
references:
https://learn.microsoft.com/en-us/azure/communication-services/quickstarts/email/send-email-smtp/send-email-smtp?source=recommendations&pivots=smtp-method-smtpclient
Limits for Email:
https://learn.microsoft.com/en-us/azure/communication-services/concepts/service-limits#rate-limits-for-email

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Unable to send embedded images with Azure Communication Service SMTP

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