Find code and diagrams at: https://www.elithecomputerguy.com/2019/07/send-email-notifications-from-arduino-with-php-mail-function/
You can send SMTP (email) notifications using an Arduino Uno with WiFi and a web server with PHP using the mail() function in PHP. You POST data to the web server from the Arduino and then the server can parse the POST data using PHP.
Note: The mail() function uses the email server configured on the web server. Shared hosting plans should have this setup by default. If you plan to pin up your own server you’ll need to install and configure an email server in addition to Apache and PHP.
Functional Parts in the Project:
Arduino WiFi Rev 2 – https://store.arduino.cc/usa/arduino-uno-wifi-rev2
560 Piece Jumper Wire Kit – https://amzn.to/2MsCLjL
Analog Temperature Sensor – https://amzn.to/2Rkkl3k