CODEWITHSUNDEEP
c#htmlemailsmtpclient
Yasser Shaikh
Yasser Shaikh

Reputation: 47804

Images breaking when sending mail using SmtpClient

I am sending a mail using C# using the SmtpClient class. I am doing the following things before sending the mail.

var mailMessage = new MailMessage();

model.ToAddresses.ForEach(to => mailMessage.To.Add(to));
mailMessage.Subject = "Test Email - By Yasser";

mailMessage.Body = String.Format("{0}{1}{2}",
                                    "<html><body>",
                                     GetEmailContent(model),
                                     "</body></html>");
mailMessage.IsBodyHtml = true;
return MailService.SendEmail(mailMessage);

and below is my MailService class:

public class MailService
{
    public static bool SendEmail(MailMessage mailMessage)
    {
        var smtpClient = new SmtpClient();
        try
        {
            smtpClient.Send(mailMessage);
            return true;
        }
        catch(Exception exp)
        {
            return false;
        }
    }
}

Now when I send the mail, the mail gets sent, here is what I get as the content of the mail in outlook when I press the view source. Below is the content of the email with view source (Obviously I have kept only a part of the image data)

<html>

<body>
    <h1>Test</h1>
    <h2>Hello World</h2>
    <h3>Missing close h3 tag</h3>

    <p>
        <a href="www.google.com">
            <img src="data:image/gif;base64,/9j/4AAQSkZJRgABAgEAYABgAAD/4Q8HRXhpZgAAT" />
        </a>
    </p>
</body>

</html>

So this appears broken(the images) in the mail, but when I copy this source and paste it into an editor and open the file using a browser all seems good (even the images).

Update : Added image of the mail from outlook

enter image description here

Any ideas ????

Upvotes: 8

Views: 9533

Answers (3)

Logan Doc
Logan Doc

Reputation: 11

To go along with Igor's Visual Basic Response, here is it converted to C#

   static void ProcessEmbeddingImages(ref MailMessage oMail)
    {
        Hashtable oLinkedResources = new Hashtable();
        oMail.Body = PadSrcDataImage(oMail.Body, ref oLinkedResources);
        if (oLinkedResources.Count > 0)
        {
            AlternateView oAlternateView = AlternateView.CreateAlternateViewFromString(oMail.Body, null, "text/html");
            oAlternateView.ContentId = "htmlView";
            oAlternateView.TransferEncoding = System.Net.Mime.TransferEncoding.SevenBit;

            foreach (DictionaryEntry oItem in oLinkedResources)
            {
                string[] oKey = ((string)oItem.Key).Split('-');
                int i = int.Parse(oKey[0]);
                string sExt = oKey[1];
                string sData = (string)oItem.Value;

                LinkedResource oLinkedResource = new LinkedResource(new System.IO.MemoryStream(Convert.FromBase64String(sData)));
                oLinkedResource.ContentId = "MyImg" + i;
                oLinkedResource.TransferEncoding = System.Net.Mime.TransferEncoding.Base64;
                oLinkedResource.ContentType = new System.Net.Mime.ContentType("image/" + sExt);
                oAlternateView.LinkedResources.Add(oLinkedResource);
            }

            oMail.AlternateViews.Add(oAlternateView);
        }
    }

    static string PadSrcDataImage(string sHtml, ref Hashtable oLinkedResources)
    {
        ArrayList oList = new ArrayList();
        string sSearch = @"\ssrc=['""]data:image/(.*?);base64,(.*?)['""]";

        MatchCollection oMatches = Regex.Matches(sHtml, sSearch, RegexOptions.IgnoreCase);
        foreach (Match m in oMatches)
        {
            if (m.Groups.Count >= 2)
            {
                string sExt = m.Groups[1].Value;
                string sData = m.Groups[2].Value;

                if (sData.Length > 7 && sData.EndsWith("%3D%3D"))
                {
                    // Replace trailing %3D%3D with ==
                    sData = sData.Substring(0, sData.Length - 6) + "==";
                }

                oLinkedResources.Add(oLinkedResources.Count + "-" + sExt, sData);

                int iPos1 = m.Groups[1].Index - "data:image/".Length;
                int iPos2 = m.Groups[2].Index + m.Groups[2].Length;
                int[] iPoints = { iPos1, iPos2 };
                oList.Add(iPoints);
            }
        }

        string sRet = "";

        if (oList.Count == 1) // One img
        {
            int[] iPoints = (int[])oList[0];
            string sStr1 = sHtml.Substring(0, iPoints[0]);
            string sStr2 = sHtml.Substring(iPoints[1]);
            sRet = sStr1 + "cid:MyImg0" + sStr2;
        }
        else if (oList.Count > 1)
        {
            for (int i = 0; i < oList.Count; i++)
            {
                int[] iPoints = (int[])oList[i];
                int iPos1 = iPoints[0];

                if (i == 0)
                {
                    // First img
                    string sStr1 = sHtml.Substring(0, iPos1);
                    sRet += sStr1 + "cid:MyImg" + i;
                }
                else // Rest imgs
                {
                    int iPrevPos2 = ((int[])oList[i - 1])[1];
                    string sStr1 = sHtml.Substring(iPrevPos2, iPos1 - iPrevPos2);
                    sRet += sStr1 + "cid:MyImg" + i;

                    if (i == oList.Count - 1) // Last
                    {
                        sRet += sHtml.Substring(iPoints[1]);
                    }
                }
            }
        }

        if (!string.IsNullOrEmpty(sRet))
        {
            return sRet;
        }
        else
        {
            return sHtml;
        }
    }

Upvotes: 0

Igor Krupitsky
Igor Krupitsky

Reputation: 885

Here is a function that will fix the problem. Call it before you SendEmail like:

ProcessEmbeddingImages(mailMessage);
return MailService.SendEmail(mailMessage);

The ProcessEmbeddingImages function is written in VB.Net so you might want to translate it to c# using one of those online translators.

Private Sub ProcessEmbeddingImages(ByRef oMail As System.Net.Mail.MailMessage)
    Dim oLinkedResources As New Hashtable()
    oMail.Body = PadSrcDataImage(oMail.Body, oLinkedResources)
    If oLinkedResources.Count > 0 Then

        Dim oAlternateView As System.Net.Mail.AlternateView = System.Net.Mail.AlternateView.CreateAlternateViewFromString(oMail.Body, Nothing, "text/html")
        oAlternateView.ContentId = "htmlView"
        oAlternateView.TransferEncoding = Net.Mime.TransferEncoding.SevenBit

        For Each oItem As DictionaryEntry In oLinkedResources
            Dim oKey As String() = Split(oItem.Key, "-")
            Dim i As Integer = oKey(0)
            Dim sExt As String = oKey(1)
            Dim sData As String = oItem.Value

            Dim oLinkedResource As New System.Net.Mail.LinkedResource(New IO.MemoryStream(System.Convert.FromBase64String(sData)))
            oLinkedResource.ContentId = "MyImg" & i
            oLinkedResource.TransferEncoding = Net.Mime.TransferEncoding.Base64
            oLinkedResource.ContentType = New System.Net.Mime.ContentType("image/" & sExt)
            oAlternateView.LinkedResources.Add(oLinkedResource)
        Next

        oMail.AlternateViews.Add(oAlternateView)
    End If
End Sub

Private Function PadSrcDataImage(ByVal sHtml As String, ByRef oLinkedResources As Hashtable) As String

    Dim oList As New ArrayList
    Dim sSearch As String = "\ssrc=['""]data:image/(.*?);base64,(.*?)['""]"

    Dim oMatches As System.Text.RegularExpressions.MatchCollection = System.Text.RegularExpressions.Regex.Matches(sHtml, sSearch, System.Text.RegularExpressions.RegexOptions.IgnoreCase)
    For Each m As System.Text.RegularExpressions.Match In oMatches
        If m.Groups.Count >= 2 Then
            Dim sExt As String = m.Groups(1).Value
            Dim sData As String = m.Groups(2).Value

            If sData.Length > 7 AndAlso Right(sData, 6) = "%3D%3D" Then
                'Replace trailing %3D%3D with ==
                sData = Left(sData, sData.Length - 6) & "=="
            End If

            oLinkedResources.Add(oLinkedResources.Count & "-" & sExt, sData)

            Dim iPos1 As Integer = m.Groups(1).Index - "data:image/".Length
            Dim iPos2 As Integer = m.Groups(2).Index + m.Groups(2).Length
            Dim iPoints As Integer() = {iPos1, iPos2}
            oList.Add(iPoints)
        End If
    Next

    Dim sRet As String = ""

    If oList.Count = 1 Then 'One img
        Dim iPoints As Integer() = oList(0)
        Dim sStr1 As String = sHtml.Substring(0, iPoints(0))
        Dim sStr2 As String = sHtml.Substring(iPoints(1))
        sRet = sStr1 & "cid:MyImg0" & sStr2

    ElseIf oList.Count > 1 Then

        For i As Integer = 0 To oList.Count - 1
            Dim iPoints As Integer() = oList(i)
            Dim iPos1 As Integer = iPoints(0)

            If i = 0 Then
                'First img
                Dim sStr1 As String = sHtml.Substring(0, iPos1)
                sRet += sStr1 & "cid:MyImg" & i

            Else 'Rest imgs
                Dim iPrevPos2 As Integer = oList(i - 1)(1)
                Dim sStr1 As String = sHtml.Substring(iPrevPos2, iPos1 - iPrevPos2)
                sRet += sStr1 & "cid:MyImg" & i

                If i = oList.Count - 1 Then    'Last
                    sRet += sHtml.Substring(iPoints(1))
                End If
            End If
        Next
    End If

    If sRet <> "" Then
        Return sRet
    Else
        Return sHtml
    End If
End Function

Upvotes: 3

Yasser Shaikh
Yasser Shaikh

Reputation: 47804

This is what I tried and works for me, tested in outlook, thunderbird and gmail. WORKS FINE !

You might want to check out the following resources I referred to make this happen :

Sample Code :

// we need to use the prefix 'cid' in the img src value
string emailReadyHtml = string.empty;
emailReadyHtml += "<p>Hello World, below are two embedded images : </p>";
emailReadyHtml += "<img src=\"cid:yasser\" >";
emailReadyHtml += "<img src=\"cid:smile\" >";

MailMessage mailMessage = new MailMessage();

mailMessage.To.Add("[email protected]");
mailMessage.From = new MailAddress("[email protected]", "Info");

mailMessage.Subject = "Test Mail";
mailMessage.IsBodyHtml = true;

string image1Path = HttpContext.Current.Server.MapPath("~/Content/images/yasser.jpg");
byte[] image2Bytes = someArrayOfByte;

ContentType c = new ContentType("image/jpeg");

// create image resource from image path using LinkedResource class.
LinkedResource linkedResource1 = new LinkedResource(imagePath);
linkedResource1.ContentType = c ;
linkedResource1.ContentId = "yasser";
linkedResource1.TransferEncoding = TransferEncoding.Base64;

// the linked resource can be created from bytes also, which may be stored in database (which was my case)
LinkedResource linkedResource2 = new LinkedResource(new MemoryStream(image2Bytes));
linkedResource2.ContentType = c;
linkedResource2.ContentId = "smile";
linkedResource2.TransferEncoding = TransferEncoding.Base64;

AlternateView alternativeView = AlternateView.CreateAlternateViewFromString(emailReadyHtml, null, MediaTypeNames.Text.Html);

alternativeView.ContentId = "htmlView";
alternativeView.TransferEncoding = TransferEncoding.SevenBit;

alternativeView.LinkedResources.Add(linkedResource1) ;
alternativeView.LinkedResources.Add(linkedResource2);

mailMessage.AlternateViews.Add(alternativeView);

SmtpClient smtpClient = new SmtpClient();
smtpClient.Send(mailMessage);

Upvotes: 16

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