Local SMTP Relay Setup (For Gmail/Outlook)

If you need to use Gmail or Outlook, create an SMTP relay on a Raspberry Pi or PC:

Postfix on Raspberry Pi

# Install Postfix
sudo apt install postfix mailutils

# Configure as a relay to Gmail
sudo nano /etc/postfix/main.cf

# Add:
# relayhost = [smtp.gmail.com]:587
# smtp_sasl_auth_enable = yes
# smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
# smtp_sasl_security_options = noanonymous
# smtp_tls_security_level = encrypt

Arduino connects to the Raspberry Pi:

// Arduino → Raspberry Pi (no SSL) → Gmail (with SSL)
EMailSender emailSend("your@gmail.com", "apppassword",
                      "your@gmail.com", "Arduino",
                      "192.168.1.100",  // IP of the Raspberry Pi
                      25);              // Local port without SSL