<system.net>
    <mailSettings>
      <smtp from="myOffice365account">
        <network host="smtp.office365.com" port="587" password="myPassword" userName="myOffice365account" defaultCredentials="false" enableSsl="true" />
      </smtp>
    </mailSettings>
  </system.net>

public bool SendMail(string[] to, string subject, string body,Attachment attachement=null)
        {
            MailMessage mail = new MailMessage();
            mail.Subject = subject;
            mail.Body = body;
            mail.IsBodyHtml = true;
            mail.BodyEncoding = Encoding.UTF8;
            mail.SubjectEncoding = System.Text.Encoding.Default;
            mail.From = new MailAddress(ConfigurationManager.AppSettings["Email_FromAddress"]);
            if (attachement !=null)
            {

                mail.Attachments.Add(attachement);
            }

                mail.To.Add(string.Join(",", to));

            SmtpClient mailClient = new SmtpClient();
            mailClient.Send(mail);
            return true;
        }