Okey,
login to your server/cpanel and open inc/header.inc.php and look after this:
$site['email'] = "your_username@your_domain_name.com";
$site['email_notify'] = "your_username@your_domain_name.com";
$site['bugReportMail'] = "your_username@your_domain_name.com";

Have you make a email account on your server for this user:
your_username@your_domain_name.com

If not make a new user account, go to Email Accounts in your cpanel an create it.

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open see more the .htacces file in the perodic directory and copy it and post it here so I can se what's inside it.