C# sendmail task

Question

I am trying to use a task on a SSIS package to send out an email using C# as the sendmail task wouldn't work (not set up to port 25 but 587).

this is the code that I have found (I know very little for C#) and I have tried:

#region Namespaces
using System;
using System.Data;
using Microsoft.SqlServer.Dts.Runtime;
using System.Windows.Forms;
using System.Net;
using System.Net.Mail;
#endregion

namespace ST_73a495fd8aa540bcb5fc84ccdf3b837a
{
    [Microsoft.SqlServer.Dts.Tasks.ScriptTask.SSISScriptTaskEntryPointAttribute]
    public partial class ScriptMain : Microsoft.SqlServer.Dts.Tasks.ScriptTask.VSTARTScriptObjectModelBase
    {
        public void Main()
        {
            MailMessage mail = new MailMessage();
            SmtpClient SmtpServer = new SmtpClient("smtp.office365.com");
            mail.From = new MailAddress("xxx@xx.xx");
            mail.To.Add("xxx@xx.xx");
            mail.Subject = "Test Mail - 1";
            mail.Body = "mail with attachment";

            System.Net.Mail.Attachment attachment;
            attachment = new System.Net.Mail.Attachment("x:/...test.csv");
            mail.Attachments.Add(attachment);

            SmtpServer.Port = 587;
            SmtpServer.Credentials = new System.Net.NetworkCredential("xxx@xx.xx", "testpassword");
            SmtpServer.EnableSsl = true;

            Dts.TaskResult = (int)ScriptResults.Success;
        }

        #region ScriptResults declaration
        enum ScriptResults
        {
            Success = Microsoft.SqlServer.Dts.Runtime.DTSExecResult.Success,
            Failure = Microsoft.SqlServer.Dts.Runtime.DTSExecResult.Failure
        };
        #endregion

    }
}

when trying to run this in the SSIS package after some time I get this error:

   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)
   at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.RuntimeType.InvokeMember(String name, BindingFlags bindingFlags, Binder binder, Object target, Object[] providedArgs, ParameterModifier[] modifiers, CultureInfo culture, String[] namedParams)
   at Microsoft.SqlServer.Dts.Tasks.ScriptTask.VSTATaskScriptingEngine.ExecuteScript()

Any ideas on what I can do to resolve this?