Method send_email

demo_example/smtp/smtp_client.cpp:167–219

    void set_email_data(const email_data &data) { data_ = data; }

    async_simple::coro::Lazy<void> send_email() {
        std::string host = server_.server;
        size_t pos = host.find("://");
        if (pos != std::string::npos) {
            host.erase(0, pos + 3);
        }

        asio::ip::tcp::resolver::query qry(
            host, server_.port, asio::ip::resolver_query_base::numeric_service);
        std::error_code ec;
        auto endpoint_iterator = resolver_.resolve(qry, ec);

        ec = co_await async_connect(io_context_, socket_, host, server_.port);
        if (ec) {
            std::cout << "Connect error: " << ec.message() << '\n';
            throw asio::system_error(ec);
        }

        std::cout << "connect ok\n";
        if constexpr (IS_SSL) {
            upgrade_to_ssl();
        }

        build_request();

        const char *header = asio::buffer_cast<const char *>(request_.data());
        std::cout << header << '\n';
        [[maybe_unused]] auto [write_ec, size] = co_await async_write(
            get_socket(), asio::buffer(header, request_.size()));
        if (write_ec) {
            std::cout << "write failed, reason: " << ec.message() << '\n';
            throw asio::system_error(write_ec);
        }

        while (true) {
            const int max_length = 1024;
            char read_buf[max_length];
            [[maybe_unused]] auto [read_ec, size] = co_await async_read_some(
                get_socket(), asio::buffer(read_buf, max_length));
            if (read_ec) {
                std::cout << "read failed, reason: " << ec.message() << '\n';
                throw asio::system_error(read_ec);
            }

            std::string_view content(read_buf, size);
            std::cout << content;

            if (content.find("250 Mail OK") != std::string_view::npos) {
                std::cout << "end smtp\n";
                break;
            }
        }
    }

private:
    auto &get_socket() {