Specify STARTTLS credentials in XML file which is called by a C# program

[lee212121]

We have an old program which i believe is built using C# for which i have the source code but i cannot edit the program. The issue is we have moved our email to a new provider who is using STARTTLS for sending emails and our program is now failing to send a simple email and returning the error below;

sendemail - Error in processing. The server response was: 5.7.3 STARTTLS is required to send mail [LO4P123CA0676.GBRP123.PROD.OUTLOOK.COM]

We have an XML file which we can change the values of but i cannot see anywhere to add anything to allow the STARTTLS to work.

The XML file contains the following;

<Sage200_ImportSLsettings>
<FileLocation>
<FileLocation>D:\Sage\Sage Import Files</FileLocation>
<Company>Volmary Ltd</Company>
<MailServer>smtp-mail.outlook.com</MailServer>
<MailTo>email</MailTo>
<MailFrom>email</MailFrom>
</FileLocation>
</Sage200_ImportSLsettings>

The C# code is shown below (which we are not able to edit)

private void ReadXMLforConnectionDetails()
        {
            try
            {
                string path = Path.GetDirectoryName(Application.ExecutablePath) + @"\@CPS_Sage200_SLImport.xml";
                if (File.Exists(path))
                {
                    IEnumerator enumerator;
                    XmlDocument document = new XmlDocument();
                    document.Load(path);
                    XmlNamespaceManager nsmgr = new XmlNamespaceManager(document.NameTable);
                    XmlNodeList list = document.DocumentElement.SelectNodes("/Sage200_ImportSLsettings/FileLocation", nsmgr);
                    try
                    {
                        XmlNode current;
                        enumerator = list.GetEnumerator();
                        goto TR_0018;
                    TR_0008:
                        try
                        {
                            this.MailFrom = current["MailFrom"].InnerText;
                        }
                        catch (Exception exception5)
                        {
                            ProjectData.SetProjectError(exception5);
                            this.MailFrom = "";
                            ProjectData.ClearProjectError();
                        }
                        goto TR_0018;
                    TR_000B:
                        try
                        {
                            this.MailTo = current["MailTo"].InnerText;
                        }
                        catch (Exception exception4)
                        {
                            ProjectData.SetProjectError(exception4);
                            this.MailTo = "";
                            ProjectData.ClearProjectError();
                        }
                        goto TR_0008;
                    TR_000E:
                        try
                        {
                            this.MailServer = current["MailServer"].InnerText;
                        }
                        catch (Exception exception3)
                        {
                            ProjectData.SetProjectError(exception3);
                            this.MailServer = "";
                            ProjectData.ClearProjectError();
                        }
                        goto TR_000B;
                    TR_0011:
                        try
                        {
                            this.SageCompany = current["Company"].InnerText;
                        }
                        catch (Exception exception2)
                        {
                            ProjectData.SetProjectError(exception2);
                            this.SageCompany = "";
                            ProjectData.ClearProjectError();
                        }
                        goto TR_000E;
                    TR_0018:
                        while (true)
                        {
                            if (enumerator.MoveNext())
                            {
                                current = (XmlNode) enumerator.Current;
                                try
                                {
                                    this.FileLocation = current["FileLocation"].InnerText;
                                }
                                catch (Exception exception1)
                                {
                                    ProjectData.SetProjectError(exception1);
                                    this.FileLocation = "";
                                    ProjectData.ClearProjectError();
                                }
                            }
                            else
                            {
                                this.ConnecttoSage200();
                                return;
                            }
                            break;
                        }
                        goto TR_0011;
                    }
                    finally
                    {
                        if (enumerator is IDisposable)
                        {
                            (enumerator as IDisposable).Dispose();
                        }
                    }
                }
                this.WritetoErrorLog("ReadXMLforConnectionDetails() - File does not exist. " + path);
                Application.Exit();
            }
            catch (Exception exception6)
            {
                Exception ex = exception6;
                ProjectData.SetProjectError(ex);
                Exception exception = ex;
                this.WritetoErrorLog("ReadXMLforConnectionDetails() - " + exception.Message);
                Application.Exit();
                ProjectData.ClearProjectError();
            }
        }

        private void sendemail(string MailSubject, string Emailbody)
        {
            try
            {
                MailMessage message = new MailMessage();
                SmtpClient client = new SmtpClient(this.MailServer);
                message.From = new MailAddress("\"CPS - Sage200 SL Import\"<" + this.MailFrom + ">");
                message.To.Add(new MailAddress(this.MailTo));
                message.Subject = MailSubject;
                message.IsBodyHtml = false;
                message.Body = Emailbody;
                client.Credentials = new NetworkCredential("email", "password");
                client.Send(message);
                message.Dispose();
            }
            catch (Exception exception1)
            {
                Exception ex = exception1;
                ProjectData.SetProjectError(ex);
                Exception exception = ex;
                this.WritetoErrorLog("sendemail - " + exception.Message);
                Application.Exit();
                ProjectData.ClearProjectError();
            }
        }

Any advice will be greatly appreciated.