Regex for matching email addresses

email_address_regex.txt

^[\w.%+-]+@(?:[\w-]+\.)+[A-Za-z]{2,4}$

Explanation:
^                   # Start of string. If searching in-line replace with \b
    [\w.%+-]+       # Matches alphanumeric, _, ., %, +, or - repeatedly
    @               # name-domain separator
    (?:
        [\w-]+      # Matches alphanumeric or - repeatedly
        \.          # Matches dot in domain separator
    )+              # Matches for one domain or for multiple subdomains
    [A-Za-z]{2,4}   # Matches top-level domain, no more than four characters
$