Errors when sending email attachments from SQL

Using the below code, I load the IDs of some photos which have been tagged for Download and loaded into a Session var. I then query the DB and attach the files before sending the email. This always works when I send 2 photos but always seems to not work at 3 photos. Instead of a proper email with attachments, I just get an e-mail with the word _Overflow_ in it. Any ideas would be appreciated.

Code:

Sub SendMail()

        Dim strFrom = "[email protected]"
        Dim strTo = Session("Download_Email")
        Dim MailMsg As New MailMessage(New MailAddress(strFrom.Trim()), New MailAddress(strTo))
        MailMsg.BodyEncoding = Encoding.Default
        MailMsg.Subject = "ACOImagery - Photos Tagged for download"
        MailMsg.Body = "The attached photos were tagged for download by " & Session("Download_Email")
        MailMsg.Priority = MailPriority.High

        Dim objConn As New SqlConnection(sConn)
        Dim strSql As String = ""

        Dim AddFilesToDownloadArray As ArrayList
        AddFilesToDownloadArray = New ArrayList

        strSql = " SELECT id_img, img_size, img_image, img_filename, exif_title FROM [img] "

        AddFilesToDownloadArray = Session("AddFilesToDownload")

        'Check to make sure an ID can only be added once!
        strSql += " WHERE "
        For x = 0 To AddFilesToDownloadArray.Count - 1
            strSql += " id_img = " & AddFilesToDownloadArray(x)
            If x < (AddFilesToDownloadArray.Count - 1) Then
                strSql += " OR"
            End If
        Next

        strSql += " ORDER by id_img DESC"

        Dim objCommand As SqlCommand
        Dim objDataReader As SqlDataReader
        Dim objConnection As SqlConnection

        objConnection = New SqlConnection(sConn)
        objCommand = New SqlCommand(strSql, objConnection)
        Try
            If objConnection.State = ConnectionState.Closed Then
                objConnection.Open()

            End If
            objDataReader = objCommand.ExecuteReader(CommandBehavior.CloseConnection)

            Do While objDataReader.Read

                Dim strMem As System.IO.MemoryStream = New System.IO.MemoryStream(CType(objDataReader("img_image"), Byte()))
                Dim strWriter As System.IO.StreamWriter = New System.IO.StreamWriter(strMem)

                strWriter.Flush()
                strMem.Position = 0

                Dim attachment As System.Net.Mail.Attachment = New System.Net.Mail.Attachment(strMem, objDataReader("img_filename"), "image/jpeg")
                MailMsg.Attachments.Add(attachment)

            Loop

        Catch ex As Exception
            lblstatus.Text = ex.Message
        Finally

            objConnection.Close()
        End Try

        ' Close the database connection if it is still open.
        If objConnection.State = ConnectionState.Open Then
            objConnection.Close()
        End If

        MailMsg.IsBodyHtml = True
        'Smtpclient to send the mail message
        Dim SmtpMail As New SmtpClient
        SmtpMail.Host = "localhost"
        SmtpMail.Send(MailMsg)

    End Sub

 

Less than 1mb each? I suppose this could be a possibility though, as I was testing locally with a free smtp, I hadn't thought of that.