$re = '/<[^<>]*>(*SKIP)(*F)|[A-Z0-9._%+-]+@([A-Z0-9.-]+\.[A-Z]{2,4}|[A-Z0-9.-]+)/mi';
$str = '<div data="example1@dom.com,example4@dom.com"><a href="example1@dom.com" > example4@dom.com, <b>example3@dom.com</b> other text, example7@dom.com, ,<i>example5@dom.com</i></a></div >
';
$subst = "[---]";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php