Regular expressions are validators of user input. Verification of user inputs are very important because they provide error messages, if you just send an email

Regular expressions are validators of user input. Verification of user inputs are very important because they provide error messages, if you just send an email and it fails it can be for many reasons: 1. The user made a mistake when typing the email. 2. Some internal server failed to send the email. Without an error, the user will never know what went wrong.