Problem with sending email using Arduino

[star24]

Hello there.
I am trying to send an email using Arduino, Ethernet Shield and SMTP service.
in the serial monitor it said that the email was sent, but when I check both the sender and receiver emails I do not find any.
Do you have any idea about the reason?
Thank you for your help.

#include <SPI.h>
#include <Ethernet.h>
#include <EthernetClient.h>

// MAC address for the Ethernet shield
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
// Network configuration
IPAddress ip(192, 168, 0, 36); // Replace with your static IP address
IPAddress dns(192, 168, 0, 1); // Replace with your DNS server IP address
IPAddress gateway(192, 168, 0, 1); // Replace with your gateway/router IP address
IPAddress subnet(255, 255, 255, 0); // Replace with your subnet mask

// SMTP server settings
const char* smtpServer = "mail.smtp2go.com";
const int smtpPort = 8465;
const char* smtpUser = "****";  // Replace with your SMTP2GO username
const char* smtpPass = "*****";  // Replace with your SMTP2GO password

// Email settings
const char* fromEmail = "******";  // Replace with your email address
const char* toEmail = "*******";  // Replace with the recipient's email address
const char* subject = "Pin 8 Triggered!";
const char* message = "The input on pin 8 was triggered.";

EthernetClient client;

void setup() {
  Serial.begin(9600);

  // Initialize pin 8 as an input
  pinMode(8, INPUT);

  // Initialize the Ethernet shield
  if (Ethernet.begin(mac) == 0) {
    Serial.println("Failed to configure Ethernet using DHCP");
    // Try with static IP
    Ethernet.begin(mac, ip, dns, gateway, subnet);
  } else {
    Serial.println("Ethernet configured via DHCP");
  }

  // Allow the hardware to start up
  delay(1000);

  Serial.println("Network configuration:");
  Serial.print("IP Address: ");
  Serial.println(Ethernet.localIP());
  Serial.print("Subnet Mask: ");
  Serial.println(Ethernet.subnetMask());
  Serial.print("Gateway: ");
  Serial.println(Ethernet.gatewayIP());
  Serial.print("DNS Server: ");
  Serial.println(Ethernet.dnsServerIP());
}

void loop() {
  // Check if pin 8 is HIGH
  if (digitalRead(8) == HIGH) {
    sendEmail();
    delay(10000);  // Delay to prevent multiple emails being sent in quick succession
  }
}

void sendEmail() {
  Serial.println("Connecting to SMTP server...");

  if (client.connect(smtpServer, smtpPort)) {
    Serial.println("Connected to SMTP server");

    // Sending email headers
    client.println("EHLO smtp2go.com");
    readResponse();
    client.println("AUTH LOGIN");
    readResponse();
    client.println(encodeBase64(smtpUser));
    readResponse();
    client.println(encodeBase64(smtpPass));
    readResponse();

    // Sending email content
    client.println("MAIL FROM:<" + String(fromEmail) + ">");
    readResponse();
    client.println("RCPT TO:<" + String(toEmail) + ">");
    readResponse();
    client.println("DATA");
    readResponse();
    client.println("Subject: " + String(subject));
    client.println("To: " + String(toEmail));
    client.println("From: " + String(fromEmail));
    client.println();
    client.println(String(message));
    client.println(".");
    readResponse();
    client.println("QUIT");
    readResponse();

    Serial.println("Email sent");
  } else {
    Serial.println("Failed to connect to SMTP server");
  }

  client.stop();
}

void readResponse() {
  while (client.connected()) {
    if (client.available()) {
      char c = client.read();
      Serial.print(c);
    }
  }
}

String encodeBase64(const char* input) {
  const char* base64_chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  String encoded;
  int i = 0, j = 0;
  unsigned char char_array_3[3], char_array_4[4];

  while (*input) {
    char_array_3[i++] = *(input++);
    if (i == 3) {
      char_array_3_to_4(char_array_3, char_array_4);
      for (i = 0; (i < 4); i++) {
        encoded += base64_chars[char_array_4[i]];
      }
      i = 0;
    }
  }

  if (i) {
    for (j = i; j < 3; j++) {
      char_array_3[j] = '\0';
    }
    char_array_3_to_4(char_array_3, char_array_4);
    for (j = 0; (j < i + 1); j++) {
      encoded += base64_chars[char_array_4[j]];
    }
    while ((i++ < 3)) {
      encoded += '=';
    }
  }

  return encoded;
}

void char_array_3_to_4(unsigned char* char_array_3, unsigned char* char_array_4) {
  char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
  char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
  char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
  char_array_4[3] = char_array_3[2] & 0x3f;
}

[docdoc]

@star24

when I check both the sender and receiver emails I do not find any

Well, first of all on the sender mailbox you can't see anything sent from another mail server so it's a pointless check.

Second, posting here the real serial output could help us better understand the commands sent and the server replies (mask any email address or password before!) .

Third, even if the server replied with an OK it doesn't mean "the email has been sent" but just" Ok, i received your email, i have put it in my email queue waiting to be processed". If any error arises, the description will be in the mail server logs, and your email discarded.

So, if everything looks nominal but you don't receive any email in the recipient's inbox, the problem must be investigated on "smtp2go" side, starting with a check of your account, settings and logs (I never used SMTP2go btw I suppose you can monitor your account data...).