code: def send(self, to, subject=None, body=None, reply_to=None, template=None, **kwargs):
          
          sender = self.config.get("MAIL_SENDER")
          recipients = [to] if not isinstance(to, list) else to
          kwargs.update({
              "subject": subject,
              "body": body,
              "reply_to": reply_to
          })
  
          if not self.validated:
              abort("MailmanConfigurationError")
  
          if self.provider == "SES":
              kwargs["to"] = recipients
              if template:
                  self.mail.send_template(template=template, **kwargs)
              else:
                 self.mail.send(**kwargs)
  
          elif self.provider == "SMTP":
              if template:
                  data = self._template(template=template, **kwargs)
                  kwargs["subject"] = data["subject"]
                  kwargs["body"] = data["body"]
              kwargs["recipients"] = recipients
              kwargs["sender"] = sender
  
              # Remove invalid Messages keys
              _safe_keys = ["recipients", "subject", "body", "html", "alts",
                            "cc", "bcc", "attachments", "reply_to", "sender",
                             "date", "charset", "extra_headers", "mail_options",
                             "rcpt_options"]
              for k in kwargs.copy():
                  if k not in _safe_keys:
                      del kwargs[k]
  
              message = flask_mail.Message(**kwargs)
              self.mail.send(message)
  
          else:
              abort("MailmanUnknownProviderError")
docs: To send email
          :param to: the recipients, list or string
          :param subject: the subject
          :param body: the body
          :param reply_to: reply_to
          :param template: template, will use the templates instead
          :param kwargs: context args
          :return: bool - True if everything is ok