Redirecting simple big problem

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Better use a .htaccess redirect so you avoid even loading WP:

Options +FollowSymLinks
RewriteEngine on
RewriteRule (.*) http://www.newdomain.com [R=301,L]

If you want to keep the path after the domain, (e.g. www.olddomain.com/mypage -> www.newdomain.com/mypage) replace the last line with:

RewriteRule (.*) http://www.newdomain.com/$1 [R=301,L]