SMTP Client#

#include <join/smtpclient.hpp>

// Create message
MailMessage mail;
mail.sender(MailSender("sender@example.com", "Sender"));
mail.addRecipient(MailRecipient("recipient@example.com"));
mail.subject("Test Email");
mail.content("Hello, World!");

// Create client
SmtpClient client("smtp.example.com", 587);

// Set credentials
client.credentials("username", "password");

// Send email
if (client.send(mail) == 0)
{
    std::cout << "Email sent successfully\n";
}
else
{
    std::cerr << "Failed to send email\n";
}

// Port 25 (default)
SmtpClient client("smtp.example.com");

// Port 587 (submission with STARTTLS)
SmtpClient client("smtp.example.com", 587);

// Port 465 (default for SMTPS)
SmtpsClient client("smtp.example.com");

// Custom port
SmtpsClient client("smtp.example.com", 465);

SmtpClient client("smtp.example.com", 587);

// Set username and password
client.credentials("myusername", "mypassword");

// Send email
client.send(mail);

// Client automatically chooses based on server capabilities
client.credentials("user@example.com", "password");
client.send(mail);

// Connects unencrypted, upgrades to TLS
SmtpClient client("smtp.example.com", 587);
client.credentials("user", "password");

// Client automatically uses STARTTLS if available
client.send(mail);

// Encrypted from the start
SmtpsClient client("smtp.example.com", 465);
client.credentials("user", "password");
client.send(mail);

SmtpClient client("smtp.example.com", 587);

// Set CA certificate for verification
client.setCaFile("/etc/ssl/certs/ca-bundle.crt");

// Enable verification
client.setVerify(true);

// Or set CA path
client.setCaPath("/etc/ssl/certs/");

SmtpClient client("smtp.example.com", 587);

// Set client certificate and key
client.setCertificate("/path/to/cert.pem", "/path/to/key.pem");

SmtpClient client("smtp.example.com", 587);

// TLS 1.2 and below
client.setCipher("ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-GCM-SHA256");

// TLS 1.3
client.setCipher_1_3("TLS_AES_256_GCM_SHA384:TLS_AES_128_GCM_SHA256");

SmtpClient client("smtp.gmail.com", 587);
client.credentials("your-email@gmail.com", "app-password");
client.send(mail);

// Note: Use App Password, not regular password

SmtpClient client("smtp.office365.com", 587);
client.credentials("your-email@outlook.com", "password");
client.send(mail);

SmtpClient client("smtp.mail.yahoo.com", 587);
client.credentials("your-email@yahoo.com", "app-password");
client.send(mail);

SmtpClient client("mail.company.com", 25);
// No authentication needed for internal server
client.send(mail);

void sendNotification(const std::string& to, const std::string& message)
{
    MailMessage mail;
    mail.sender(MailSender("noreply@app.com", "App Notifications"));
    mail.addRecipient(MailRecipient(to));
    mail.subject("Notification");
    mail.content(message);

    SmtpClient client("smtp.example.com", 587);
    client.credentials("app-email@example.com", "password");

    if (client.send(mail) != 0)
    {
        std::cerr << "Failed to send notification\n";
    }
}

void sendWelcomeEmail(const User& user)
{
    MailMessage mail;

    mail.sender(MailSender("welcome@company.com", "Company Team"));
    mail.addRecipient(MailRecipient(user.email, user.name));
    mail.subject("Welcome to our service!");

    std::string content =
        "Dear " + user.name + ",\n"
        "\n"
        "Welcome to our service!\n"
        "\n"
        "To get started, please verify your email address.\n"
        "\n"
        "Best regards,\n"
        "The Team";

    mail.content(content);

    SmtpClient client("smtp.company.com", 587);
    client.credentials("noreply@company.com", "password");
    client.send(mail);
}

// Current version doesn't support attachments directly
// Workaround: Include links or embed small data

void sendReportLink(const std::string& to, const std::string& reportUrl)
{
    MailMessage mail;
    mail.sender(MailSender("reports@company.com", "Reports"));
    mail.addRecipient(MailRecipient(to));
    mail.subject("Your report is ready");

    mail.content(
        "Your report is ready for download:\n"
        "\n" +
        reportUrl + "\n"
        "\n"
        "This link will expire in 24 hours.\n"
    );

    SmtpClient client("smtp.company.com", 587);
    client.credentials("reports@company.com", "password");
    client.send(mail);
}

SmtpClient client("smtp.example.com", 587);
client.credentials("user", "password");

if (client.send(mail) == 0)
{
    std::cout << "Email sent successfully\n";
}
else
{
    std::error_code ec = join::lastError;
    std::cerr << "Send failed: " << ec.message() << "\n";
}

int result = client.send(mail);

if (result != 0)
{
    // Check specific errors
    std::error_code ec = join::lastError;

    // Connection failed
    // Authentication failed
    // Invalid recipient
    // Server rejected message

    std::cerr << "Error: " << ec.message() << "\n";
}

// Good: Use TLS (port 587 with STARTTLS)
SmtpClient client("smtp.example.com", 587);

// Good: Use SMTPS (port 465)
SmtpsClient client("smtp.example.com", 465);

// Avoid: Unencrypted (port 25)
SmtpClient client("smtp.example.com", 25);

bool validateMail(const MailMessage& mail)
{
    if (mail.sender().empty())
    {
        return false;
    }
    if (mail.recipients().empty())
    {
        return false;
    }
    if (mail.subject().empty())
    {
        return false;
    }
    return true;
}

if (validateMail(mail))
{
    client.send(mail);
}

// Good: Read from secure config
std::string user = config.getSmtpUser();
std::string pass = config.getSmtpPassword();
client.credentials(user, pass);

// Bad: Hardcoded credentials
client.credentials("hardcoded@example.com", "password123");

bool sendWithRetry(SmtpClient& client, const MailMessage& mail, int maxRetries = 3)
{
    for (int i = 0; i < maxRetries; ++i)
    {
        if (client.send(mail) == 0)
        {
            return true;
        }

        // Wait before retry
        std::this_thread::sleep_for(std::chrono::seconds(5));
    }
    return false;
}