Import allows you to import email incorrect and duplicate. It 'easy to fix I would also ask if the campaign will be sent to two identical email or the program notice me has already been sent and send only one email.
line-update.php don't check duplicate and don't check valid email edit: sorry line-update.php check duplicate but don't work
import-update.php don't check valid email :-)
Suggestion: 1) add LIMIT 1 to select query 2) add index to email (and other field you use in select) in subscribers table 3) check 2 query in import-update $q = 'SELECT email from subscribers WHERE (email = "'.$linearray[0].'" || email = " '.$linearray[1].'" || email = "'.$linearray[1].'") AND bounced = 1'; --- || email = "'.$linearray[1].'" is duplicate and slow query