Arduino - Door Open Email Notification

In this guide, we will learn how to use an Arduino to send emails when a door opens. We will explain how to set it up, what parts you need, and give you detailed steps to connect an Arduino with a door sensor and an email service. This will help keep your home secure by sending you instant email alerts when the door is opened.

Arduino Door Open Email Notification

Hardware Required

1×Arduino UNO R4 WiFi
1×USB Cable Type-C
1×Door Sensor
1×Jumper Wires
1×(Optional) DC Power Jack
1×(Optional) 9V Power Adapter for Arduino
1×(Recommended) Screw Terminal Block Shield for Arduino Uno
1×(Optional) Transparent Acrylic Enclosure For Arduino Uno

Or you can buy the following sensor kits:

1×DIYables Sensor Kit (30 sensors/displays)
1×DIYables Sensor Kit (18 sensors/displays)
Please note: These are Amazon affiliate links. If you buy the components through these links, We will get a commission at no extra cost to you. We appreciate it.

About Door Sensor and Gmail

We offer detailed tutorials on Door Sensors and Gmail. Each guide includes comprehensive details and clear, step-by-step instructions on hardware setup, the principles of operation, and how to connect and program the Arduino. You can find out more about these tutorials through these links:

Wiring Diagram between Door Sensor and Arduino

Arduino Door Sensor Wiring Diagram

This image is created using Fritzing. Click to enlarge image

Arduino Code

/* * Created by * * This example code is in the public domain * * Tutorial page: */ #include <WiFiS3.h> #include <ESP_Mail_Client.h> #define WIFI_SSID "YOUR_WIFI_SSID" // CHANGE IT #define WIFI_PASSWORD "YOUR_WIFI_PASSWORD" // CHANGE IT // the sender email credentials #define SENDER_EMAIL "" // CHANGE IT #define SENDER_PASSWORD "xxxx xxxx xxxx xxxx" // CHANGE IT to your Google App password #define RECIPIENT_EMAIL "" // CHANGE IT #define SMTP_HOST "" #define SMTP_PORT 587 #define DOOR_SENSOR_PIN 13 // Arduino pin connected to door sensor's pin int door_state; // current state of door sensor int prev_door_state; // previous state of door sensor SMTPSession smtp; void setup() { Serial.begin(9600); WiFi.begin(WIFI_SSID, WIFI_PASSWORD); Serial.print("Connecting to Wi-Fi"); while (WiFi.status() != WL_CONNECTED) { Serial.print("."); delay(300); } Serial.println(); Serial.print("Connected with IP: "); Serial.println(WiFi.localIP()); Serial.println(); pinMode(DOOR_SENSOR_PIN, INPUT_PULLUP); // set Arduino pin to input pull-up mode door_state = digitalRead(DOOR_SENSOR_PIN); // read state } void loop() { prev_door_state = door_state; // save the last state door_state = digitalRead(DOOR_SENSOR_PIN); // read new state if (prev_door_state == LOW && door_state == HIGH) { // state change: LOW -> HIGH Serial.println("The door is opened"); String subject = "Email Notification from Arduino"; String textMsg = "This is an email sent from Arduino.\n"; textMsg += "Your door is opened"; gmail_send(subject, textMsg); } else if (prev_door_state == HIGH && door_state == LOW) { // state change: HIGH -> LOW Serial.println("The door is closed"); } } void gmail_send(String subject, String textMsg) { // set the network reconnection option MailClient.networkReconnect(true); smtp.debug(1); smtp.callback(smtpCallback); Session_Config config; // set the session config config.server.host_name = SMTP_HOST; config.server.port = SMTP_PORT; = SENDER_EMAIL; config.login.password = SENDER_PASSWORD; config.login.user_domain = F(""); config.time.ntp_server = F(","); config.time.gmt_offset = 3; config.time.day_light_offset = 0; // declare the message class SMTP_Message message; // set the message headers = F("Arduino"); = SENDER_EMAIL; message.subject = subject; message.addRecipient(F("To Whom It May Concern"), RECIPIENT_EMAIL); message.text.content = textMsg; message.text.transfer_encoding = "base64"; message.text.charSet = F("utf-8"); message.priority = esp_mail_smtp_priority::esp_mail_smtp_priority_low; // set the custom message header message.addHeader(F("Message-ID: <>")); // connect to the server if (!smtp.connect(&config)) { Serial.println("Connection error: "); Serial.print("- Status Code: "); Serial.println(smtp.statusCode()); Serial.print("- Error Code: "); Serial.println(smtp.errorCode()); Serial.print("- Reason: "); Serial.println(smtp.errorReason().c_str()); return; } if (!smtp.isLoggedIn()) { Serial.println("Not yet logged in."); } else { if (smtp.isAuthenticated()) Serial.println("Successfully logged in."); else Serial.println("Connected with no Auth."); } // start sending Email and close the session if (!MailClient.sendMail(&smtp, &message)) { Serial.println("Connection error: "); Serial.print("- Status Code: "); Serial.println(smtp.statusCode()); Serial.print("- Error Code: "); Serial.println(smtp.errorCode()); Serial.print("- Reason: "); Serial.println(smtp.errorReason().c_str()); } } // callback function to get the Email sending status void smtpCallback(SMTP_Status status) { // print the current status Serial.println(; // print the sending result if (status.success()) { for (size_t i = 0; i < smtp.sendingResult.size(); i++) { // get the result item SMTP_Result result = smtp.sendingResult.getItem(i); Serial.print("Status: "); if (result.completed) Serial.println("success"); else Serial.println("failed"); Serial.print("Recipient: "); Serial.println(result.recipients.c_str()); Serial.print("Subject: "); Serial.println(result.subject.c_str()); } Serial.println("----------------\n"); // free the memory smtp.sendingResult.clear(); } }

Quick Steps

  • If this is the first time you use Arduino Uno R4, see how to setup environment for Arduino Uno R4 on Arduino IDE.
  • Attach the door sensor to your door.
  • Link the Arduino board with the door sensor.
  • Connect the Arduino board to your computer using a micro USB cable.
  • Launch the Arduino IDE on your computer.
  • Select the right Arduino board (Arduino Uno R4 WiFi) and COM port.
  • In Arduino IDE, click on the "Library Manager" icon on the left menu to open it.
  • Type ESP Mail Client in the search box, and look for ESP Mail Client by Mobizt.
  • Press the Install button to add the ESP Mail Client library.
Arduino ESP Mail Client library
  • Copy the provided code and open it using Arduino IDE.
  • Update your WiFi details (network name and password) in the code. Change the values of WIFI_SSID and WIFI_PASSWORD to your own.
  • Edit the sender's email and password in the code. Modify SENDER_EMAIL and SENDER_PASSWORD.


Make sure the sender's email is from Gmail. Use the App password from the previous step as the sender's password. The recipient's email can be any email type.

  • Press the Upload button in Arduino IDE to upload the code to the Arduino
  • Open the Serial Monitor
  • Open the door
  • View the results on the Serial Monitor.
The door is opened #### Email sent successfully > C: Email sent successfully ---------------- Message sent success: 1 Message sent failed: 0 ---------------- Message No: 1 Status: success Date/Time: May 27, 2024 04:42:50 Recipient: Subject: Email Notification from Arduino ----------------
Autoscroll Show timestamp
Clear output
9600 baud  
  • Look in your recipient's email inbox. You will receive an email similar to the following:
Arduino door sensor email

Video Tutorial

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