Invalid email address

An invalid email address is an email address that does not conform to the standard format of an email address or is not recognized by the email server. Here are some common reasons why an email address may be considered invalid:

  1. Incorrect syntax: The email address may have an incorrect syntax, such as missing or extra characters, or incorrect use of special characters like @,., or -.
  2. Non-existent domain: The domain part of the email address may not exist or may be misspelled.
  3. Invalid characters: The email address may contain invalid characters, such as spaces, special characters, or non-ASCII characters.
  4. Too long or too short: The email address may be too long or too short, exceeding the maximum allowed length or characters.
  5. Typo or misspelling: The email address may contain a typo or misspelling, making it impossible to deliver the email.

Examples of invalid email addresses include:

To validate an email address, you can use various techniques, such as:

  1. Regular expressions: Use a regular expression to check if the email address conforms to the standard format.
  2. Email validation libraries: Use a library or framework that provides email validation functionality, such as PHP's filter_var() function or JavaScript's email regular expression.
  3. SMTP validation: Send a test email to the address and check if it is delivered successfully.

Remember that email validation is not foolproof, and it's possible for an invalid email address to pass validation. However, using a combination of these techniques can help you identify and reject invalid email addresses.