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Sending Email using ESP8266 Wi-Fi (Node MCU) Module via SMTP

ESP8266
WiFi
Email
NODEMCU
SMTP
SMTP-Arduino
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In this Blog I will explain how to send Email using ESP8266 Wifi Module.

I will use mailgun SMTP Server for this purpose. 

If you want to test only you can login free or you can use other SMTP services also.

First I will login to my mailgun account and notedown my SMTP servername, port, email and password.

You will find these credentials in every smtp service.

 

Download Code

 

SMTP -

SMTP stands for Simple Mail Transfer Protocol which is used for transfer the mail via internet. 

Read More About SMTP On Wikipedia

 

SMTP Basic Commands -

More about SMTP Command

 

How to implement all these idea in Esp8266 -

First use esp8266wifi library function for making connection with SMTP mail server.

If it will connect successfully. Server return 220 response code.

Now send HELO or EHLO to verify connection.

After this authenticate by sending username and password using AUTH LOGIN command. 

After successfull authentication you will logged in.

Next you need to send FROM and RCPT TO command .

Now send DATA command so that it will ready for taking data input.

Now send  . (dot)  for terminate data transfer and send email.

Now Quit connection by sending command QUIT

 

I have used these commands because smtp understand these commands.

 

What we need ( Requirements ) -

  1. ESP8266
  2. esp8266Wifi.h library
  3. Arduino IDE or anyother

Steps -

I have divided it into 5 step according to my program. 

• Step 1 -

Notedown the ServerName( host ) , Port, Username( Email ) , Password. 

Go to code and insert it into right place. 

Write Sender details, receiver details, subject, message. 

Connect with your SSID and Password. 

 

• Step 2 -

Now next We declare WebClient Object. 

WiFiClient SMTPClient;

 

• Step 3 -

The function Response() checks if any data is available from server and print server response on serial monitor. 

We are going to use this function for checking server response after each send command so that we can verify that everything is going in proper way. 

 

• Step 4 -

Now in function SendSmtpMail(). 

first connect with smtp servername and port and checking for response of server. 

SMTPClient.connect(host, port)

If it is connected successfully with server, the server send 220 code in response.

Now next according to Smtp we have to send "HELO"( IN SMTP) and "EHLO" ( Extended SMTP )

SMTPClient.println("HELO")

For this input command server send 250 response code if it is successful. 

Now we login by sending SMTP command "AUTH LOGIN". 

SMTPClient.println("AUTH LOGIN");

The server respond with code 334 incating that server is ready for taking username.

Now we send base64 encoded username .   

  SMTPClient.println(senderEncodedEmail);

The server respond with 334 incating username accepted and ready for taking password . 

Send base64 encoded password .

  SMTPClient.println(senderEncodedPassword);

The server respond with code 235 incating that Authentication successful. 

Now we logged in our account using SMTP. 

 

• Step 5 -

In this step we will send email message. 

After logged in, 

We will send command for indicating whom will send message. 

SMTPClient.printf("MAIL FROM: %s\n",*from);

We will send command for receiver.

SMTPClient.printf("RCPT TO: %s\n",*recipient);

We need to send DATA command to smtp server. 

SMTPClient.println(F("DATA"));

The server respond with code 354 incating that continue. It means server is ready for receiving email message with proper format. 

Note down server will recieve message line by line while you will not send "." command. 

 

Now to Send Text you should use below code. 

  SMTPClient.printf("To: %s\n",*recipient);
  SMTPClient.printf("From: %s\n",*from);  
  SMTPClient.printf("Subject: %s\n",*subject);

  SMTPClient.println(F("This message Contains Text.\n"));

If you want to send HTML mail replace above code with below code. 

  SMTPClient.printf("To: %s\n",*recipient);
  SMTPClient.printf("From: %s\n",*from);  
  SMTPClient.println("Mime-Version: 1.0");
  SMTPClient.println("Content-Type: Text/HTML; charset=ISO-8859-1");
  SMTPClient.println("Content-Transfer-Encoding: 7bit");
  SMTPClient.printf("Subject: %s\n",*subject);

  // It is neccessary to convert MAIL_TEMPLATE into String. It can't be send directly.
  String body = HTML_EMAIL_TEMPLATE;
  SMTPClient.println(body);

 

Once you send "." SMTP command to server, it will terminate receiving message further and send it. 

SMTPClient.println(F("."));

If mail send is successful you will receive 250 response. 

 

Code for sending TEXT email -

 

#include <ESP8266WiFi.h>

#define ssid "Your SSID"  // Wifi Name
#define password "Your Pass"  // Wifi Password

const char* host = "smtp.mailgun.org";   // Smtp Server name
const int port = 587;                    // Smtp port

// Base 64 Encoded Email and Password of sender.
const char* senderEncodedEmail = "base64 encoded email";
const char* senderEncodedPassword = "base64 encoded password";

// Recipient address
const char* Recipient = "mail@mail.com";

// From Name and Email.Sender Name will be shown at top of the message at receiver end.
const char* From = "NAME <mail@mail.com>";

// Subject
const char* Subject = "ESP8266 EMAIL TESTING";

// HTML Message
const char HTML_EMAIL_TEMPLATE[] PROGMEM = R"=====(
<!doctype html>
<html lang="en">

<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Learning Electronic TESTING</title>
<meta name="viewport" content="width=device-width, initial-scale=1.0" />

<style>
h1{
    margin:auto;
    color:#07B8B4;
    text-align:center;
}


</style>

</head>

<body style="margin: 0; padding: 0;">

    <h1>Learning Electronic</h1>
    <p>Hello Visitor,</p>

    <p><strong>Thank You for visiting learning electronic blog.\n</Strong></p>
    <p style="color:#a1a1a1;text-align:center;margin-top:10px;"><strong>Learning Electronic</Strong></p>

</body>

</html>

)=====";

// Creating WifiClient Object with name SMTPClient
WiFiClient SMTPClient;

// Function for sending email
void sendSmtpEmail(const char** from ,const char** recipient ,const char** subject);
// function for getting response back from server for input commands
byte Response();


void setup() {
  Serial.begin(115200);
  Serial.println();

  Serial.printf("Connecting to :");
  Serial.println(ssid);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED)
  {
    delay(300);
    Serial.print(".");
  }
  Serial.printf("\n[Connection Established with : %s]\n", ssid);

  // Calling Email Function . It will print server response on Serial Monitor
  sendSmtpEmail(&From, &Recipient, &Subject);

}

void loop() {


}


void sendSmtpEmail(const char** from ,const char** recipient ,const char** subject){

  Serial.printf("\nConnecting to %s ... ", host);
  // Checking for connection with SMTP Server
  if (SMTPClient.connect(host, port))
  {
    Response();
  }
  else{
      Serial.println("Failed");
      return 0;
  }

  // You will get 220 Response Code for successful connection.
  // In my case  "220 Mailgun Influx ready"

  SMTPClient.println("HELO");
  if(!Response()){
    Serial.println("Failed");
  }

  // You will receive 250 response with some text.
  // In my case "250 smtp-out-n05.prod.us-east-1.postgun.com"


  SMTPClient.println("AUTH LOGIN");
  if(!Response()){
    Serial.println("Failed");
  }

  // You will get 334 response . It tells that you are ready to send you base64 encoded username
  // In my case response is "334 VXNlcm5hbWU6"


  SMTPClient.println(senderEncodedEmail);
  if(!Response()){
    Serial.println("Failed");
  }

  // You will get 334 response . It tells that you are ready to send you base64 encoded password
  // In my case response is "334 UGFzc3dvcmQ6"

  SMTPClient.println(senderEncodedPassword);
  if(!Response()){
    Serial.println("Failed");
  }    

  // If authentication is successfull you will get response 235 which means Authentication successful.
  // In my case "235 Authentication successful"


  SMTPClient.printf("MAIL FROM: %s\n",*from);
  if (!Response()) {
    Serial.println("Failed");
  }

   // You will get response 250 for OK.
   //In my case     "250 Sender address accepted"



  SMTPClient.printf("RCPT TO: %s\n",*recipient);
  if (!Response()){
    Serial.println("Failed");
  }

  // You will get 250 response.
  // In my case  "250 Recipient address accepted"

  SMTPClient.println(F("DATA"));
  if (!Response()){
    Serial.println("Failed");
  }

  // You will get response 354 which means you are ready to send you data.
  // In my case "354 Continue"


  SMTPClient.printf("To: %s\n",*recipient);
  SMTPClient.printf("From: %s\n",*from);  
  
   //SMTPClient.println("Mime-Version: 1.0");
  //SMTPClient.println("Content-Type: Text/HTML; charset=ISO-8859-1");
  //SMTPClient.println("Content-Transfer-Encoding: 7bit");

  SMTPClient.printf("Subject: %s\n",*subject);

  SMTPClient.println(F("This is a Text Message.\n"));

  // It is neccessary to convert MAIL_TEMPLATE into String. It can't be send directly.
  //String body = HTML_EMAIL_TEMPLATE;
  //SMTPClient.println(body);

  SMTPClient.println(F("."));
  if (!Response()) {
     Serial.println("Failed");
  }

  // If everything is Ok you will receive successful response code 250.
  // In my case  "250 Great success"

  Serial.println("Successful... Check Your Mail!!!!!!!");

  SMTPClient.println(F("QUIT"));
  if (!Response()) {
     Serial.println("Failed");
  }
  // Received 221 code in response for successful

}


byte Response()
{
  byte responseCode;
  byte responseByte;
  int Counter = 0;

  while (!SMTPClient.available()) 
  {
    delay(1);
    Counter++;
    //Wating till 3 seconds
    if (Counter > 30000) 
    {
      SMTPClient.stop();
      Serial.println(F("\r\nTimeout"));
      return 0;
    }
  }

  responseCode = SMTPClient.peek();
  while (SMTPClient.available())
  {
    responseByte = SMTPClient.read();
    Serial.write(responseByte);
  }

  return 1;
}

 

Code for sending HTML email -

#include <ESP8266WiFi.h>

#define ssid "Your SSID"  // Wifi Name
#define password "Your Pass"  // Wifi Password

const char* host = "smtp.mailgun.org";   // Smtp Server name
const int port = 587;                    // Smtp port

// Base 64 Encoded Email and Password of sender.
const char* senderEncodedEmail = "base64 encoded email";
const char* senderEncodedPassword = "base64 encoded password";

// Recipient address
const char* Recipient = "mail@mail.com";

// From Name and Email.Sender Name will be shown at top of the message at receiver end.
const char* From = "NAME <mail@mail.com>";

// Subject
const char* Subject = "ESP8266 EMAIL TESTING";

// HTML Message
const char HTML_EMAIL_TEMPLATE[] PROGMEM = R"=====(
<!doctype html>
<html lang="en">

<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Learning Electronic TESTING</title>
<meta name="viewport" content="width=device-width, initial-scale=1.0" />

<style>
h1{
    margin:auto;
    color:#07B8B4;
    text-align:center;
}


</style>

</head>

<body style="margin: 0; padding: 0;">

    <h1>Learning Electronic</h1>
    <p>Hello Visitor,</p>

    <p><strong>Thank You for visiting learning electronic blog.\n</Strong></p>
    <p style="color:#a1a1a1;text-align:center;margin-top:10px;"><strong>Learning Electronic</Strong></p>

</body>

</html>

)=====";

// Creating WifiClient Object with name SMTPClient
WiFiClient SMTPClient;

// Function for sending email
void sendSmtpEmail(const char** from ,const char** recipient ,const char** subject);
// function for getting response back from server for input commands
byte Response();


void setup() {
  Serial.begin(115200);
  Serial.println();

  Serial.printf("Connecting to :");
  Serial.println(ssid);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED)
  {
    delay(300);
    Serial.print(".");
  }
  Serial.printf("\n[Connection Established with : %s]\n", ssid);

  // Calling Email Function . It will print server response on Serial Monitor
  sendSmtpEmail(&From, &Recipient, &Subject);

}

void loop() {


}


void sendSmtpEmail(const char** from ,const char** recipient ,const char** subject){

  Serial.printf("\nConnecting to %s ... ", host);
  // Checking for connection with SMTP Server
  if (SMTPClient.connect(host, port))
  {
    Response();
  }
  else{
      Serial.println("Failed");
      return 0;
  }

  // You will get 220 Response Code for successful connection.
  // In my case  "220 Mailgun Influx ready"

  SMTPClient.println("HELO");
  if(!Response()){
    Serial.println("Failed");
  }

  // You will receive 250 response with some text.
  // In my case "250 smtp-out-n05.prod.us-east-1.postgun.com"


  SMTPClient.println("AUTH LOGIN");
  if(!Response()){
    Serial.println("Failed");
  }

  // You will get 334 response . It tells that you are ready to send you base64 encoded username
  // In my case response is "334 VXNlcm5hbWU6"


  SMTPClient.println(senderEncodedEmail);
  if(!Response()){
    Serial.println("Failed");
  }

  // You will get 334 response . It tells that you are ready to send you base64 encoded password
  // In my case response is "334 UGFzc3dvcmQ6"

  SMTPClient.println(senderEncodedPassword);
  if(!Response()){
    Serial.println("Failed");
  }    

  // If authentication is successfull you will get response 235 which means Authentication successful.
  // In my case "235 Authentication successful"


  SMTPClient.printf("MAIL FROM: %s\n",*from);
  if (!Response()) {
    Serial.println("Failed");
  }

   // You will get response 250 for OK.
   //In my case     "250 Sender address accepted"



  SMTPClient.printf("RCPT TO: %s\n",*recipient);
  if (!Response()){
    Serial.println("Failed");
  }

  // You will get 250 response.
  // In my case  "250 Recipient address accepted"

  SMTPClient.println(F("DATA"));
  if (!Response()){
    Serial.println("Failed");
  }

  // You will get response 354 which means you are ready to send you data.
  // In my case "354 Continue"


  SMTPClient.printf("To: %s\n",*recipient);
  SMTPClient.printf("From: %s\n",*from);  
  SMTPClient.println("Mime-Version: 1.0");
  SMTPClient.println("Content-Type: Text/HTML; charset=ISO-8859-1");
  SMTPClient.println("Content-Transfer-Encoding: 7bit");
  SMTPClient.printf("Subject: %s\n",*subject);

  //SMTPClient.println(F("This message is sent from ESP8266.\n"));

  // It is neccessary to convert MAIL_TEMPLATE into String. It can't be send directly.
  String body = HTML_EMAIL_TEMPLATE;
  SMTPClient.println(body);

  SMTPClient.println(F("."));
  if (!Response()) {
     Serial.println("Failed");
  }

  // If everything is Ok you will receive successful response code 250.
  // In my case  "250 Great success"

  Serial.println("Successful... Check Your Mail!!!!!!!");

  SMTPClient.println(F("QUIT"));
  if (!Response()) {
     Serial.println("Failed");
  }
  // Received 221 code in response for successful
}


byte Response()
{
  byte responseCode;
  byte responseByte;
  int Counter = 0;

  while (!SMTPClient.available()) 
  {
    delay(1);
    Counter++;
    //Wating till 3 seconds
    if (Counter > 30000) 
    {
      SMTPClient.stop();
      Serial.println(F("\r\nTimeout"));
      return 0;
    }
  }

  responseCode = SMTPClient.peek();
  while (SMTPClient.available())
  {
    responseByte = SMTPClient.read();
    Serial.write(responseByte);
  }

  return 1;
}

If you face any problem comment it.