How to check if mail adress is valid

There are several ways to check if an email address is valid:

Use a regular expression: You can use a regular expression to validate an email address. Here's an example:
```
^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$
```
This regular expression matches most common email address formats, but it's not foolproof. You can use online tools like Regex101 to test and refine your regular expression.
Use a library or framework: Many programming languages and frameworks have built-in functions or libraries to validate email addresses. For example:
- In JavaScript, you can use the email property of the HTMLInputElement object to validate an email address.
- In Python, you can use the email module to validate an email address.
- In Java, you can use the java.util.regex package to validate an email address.
Use a third-party API: There are several third-party APIs that can validate email addresses, such as:
- EmailValidator: A JavaScript library that validates email addresses.
- EmailVerify: A Python library that validates email addresses.
- EmailValidator.net: A web-based API that validates email addresses.
Check the email address format: You can check if the email address has the correct format by checking for the following:
- It starts with a letter or a number.
- It contains only letters, numbers, dots, hyphens, and underscores.
- It has a @ symbol.
- It has a domain name (e.g., example.com) and a top-level domain (e.g., .com, .org, etc.).
- It has a maximum length of 254 characters.

Here's an example of how you can check the email address format in JavaScript:

function isValidEmail(email) {
  const re = /^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/;
  return re.test(email);
}

Keep in mind that email address validation is not foolproof, and it's possible for an email address to be valid but not actually exist.