mail and mysql confirmation of that [double-opt in]

how is the best way to check if email address is valid: is this preg_match() OK? preg_match('/^([a-zA-Z0-9])+([a-zA-Z0-9\._-])*@([a-zA-Z0-9_-])+([a-zA-Z0-9\._-]+)+$/', $email); How can I make double opt-in mail system? My idea: 1.) I remember the email entered and user data and the sha1($email); in mysql db 2.) I send email with activation link of the sha1($email); 3.) I am not clear how to proceed when the link is activated. How to update the db and submit the necessary form to the marketing. Thanks in advance, -- When the sun rises I receive and when it sets I forgive -> http://users.skavt.net/~gleskovs/ All the Love, Grega Leskov'sek