Creating a project that sends email notifications using Arduino involves using an Ethernet or WiFi shield/module to connect to the internet and an email-sending service or API. Below is a complete project outline and source code to help you set up this project.


### Project Outline

1. **Hardware Requirements**:
    - Arduino board (e.g., Arduino Uno)
    - Ethernet shield or WiFi module (e.g., ESP8266)
    - Breadboard and jumper wires (if needed)
    - Sensors (e.g., a motion sensor or temperature sensor) for the input trigger

2. **Software Requirements**:
    - Arduino IDE
    - Email-sending service or API (e.g., IFTTT, SMTP2GO)

3. **Steps**:
    1. Set up the hardware and connect the Ethernet/WiFi shield/module to the Arduino board.
    2. Configure the email-sending service (e.g., set up an IFTTT applet to send an email when a specific event is triggered).
    3. Write the Arduino code to detect sensor input and send an HTTP request to the email-sending service.

### Source Code

#### Using IFTTT for Email Notifications

1. **Set up IFTTT**:
    - Create an IFTTT account and set up a new applet.
    - Choose the "Webhooks" service as the trigger and "Send me an email" as the action.
    - Note the webhook URL and the key provided by IFTTT.

2. **Arduino Code**:

```cpp
#include  // Use for other WiFi modules like ESP32
#include

const char* ssid = "your_SSID";        // Replace with your network SSID
const char* password = "your_PASSWORD";  // Replace with your network password

const char* ifttt_server = "maker.ifttt.com";
const char* ifttt_key = "your_IFTTT_webhook_key"; // Replace with your IFTTT key
const char* event_name = "your_event_name";       // Replace with your IFTTT event name

WiFiClient client;
HTTPClient http;

void setup() {
  Serial.begin(115200);
  delay(10);
  
  // Connect to WiFi
  Serial.println();
  Serial.println();
  Serial.print("Connecting to ");
  Serial.println(ssid);
  
  WiFi.begin(ssid, password);
  
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  
  Serial.println("");
  Serial.println("WiFi connected");
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());
}

void loop() {
  // Replace with your sensor input logic
  int sensorValue = digitalRead(D2); // Example: reading a motion sensor on pin D2
  if (sensorValue == HIGH) {
    sendEmailNotification();
    delay(10000); // Delay to prevent multiple emails in quick succession
  }
}

void sendEmailNotification() {
  Serial.println("Sending email notification...");

  String url = String("/trigger/") + event_name + "/with/key/" + ifttt_key;

  if (http.begin(client, "http://" + String(ifttt_server) + url)) {
    int httpCode = http.GET();
    if (httpCode > 0) {
      Serial.printf("HTTP GET... code: %dn", httpCode);
      if (httpCode == HTTP_CODE_OK) {
        String payload = http.getString();
        Serial.println(payload);
      }
    } else {
      Serial.printf("HTTP GET... failed, error: %sn", http.errorToString(httpCode).c_str());
    }
    http.end();
  }
}
```

### Instructions to Run the Project

1. **Hardware Setup**:
    - Connect your Arduino board to the Ethernet shield or WiFi module.
    - Connect the sensor to the appropriate pin on the Arduino board.

2. **Software Setup**:
    - Install the required libraries (`ESP8266WiFi` and `ESP8266HTTPClient` for ESP8266 or `WiFi` for other modules) in the Arduino IDE.
    - Replace the placeholders (`your_SSID`, `your_PASSWORD`, `your_IFTTT_webhook_key`, `your_event_name`) with your actual WiFi credentials and IFTTT details.

3. **Upload the Code**:
    - Connect your Arduino board to your computer and upload the code using the Arduino IDE.

4. **Testing**:
    - Open the Serial Monitor to view the debug information.
    - Trigger the sensor to send an email notification through IFTTT.

This project can be extended by adding multiple sensors, logging data, or using different email-sending services or APIs.