@spec deliver(Swoosh.Email.t(), Keyword.t()) :: {:ok, term()} | {:error, term()}

@spec deliver!(Swoosh.Email.t(), Keyword.t()) :: term() | no_return()

@spec deliver_many(
  [
    %Swoosh.Email{
      assigns: term(),
      attachments: term(),
      bcc: term(),
      cc: term(),
      from: term(),
      headers: term(),
      html_body: term(),
      private: term(),
      provider_options: term(),
      reply_to: term(),
      subject: term(),
      text_body: term(),
      to: term()
    }
  ],
  Keyword.t()
) :: {:ok, term()} | {:error, term()}