When a user submits an email subscription form, the data is sent to the server where various checks are performed:
Format Validation: Ensures the email address follows the standard format (e.g., user@example.com). Domain Validation: Verifies that the domain part of the email address is valid and not blacklisted. MX Record Check: Checks if the domain has valid MX (Mail Exchange) records, indicating that it can receive emails. Duplicate Check: Ensures the email address is not already in the database to prevent duplicates. Sanitization: Removes any harmful elements from the input to protect against security threats.