$re = '/from=<(.+?)>,/m';
$str = 'Jul 10 10:09:08 srv24-s-st postfix/qmgr[3043]: 25E6CDF04F4: from=<testmail@email.ru>, size=617951, nrcpt=1 (queue active)';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
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