TYPO3 Core

Postfix uses Errors-To instead of Return-Path, so this header should be set to the value of the Return-Path header.

see t3lib_htmlmail->setHeaders():

if ($this->returnPath) {
$this->add_header("Return-Path: ".$this->returnPath);
$this->add_header("Errors-To: ".$this->returnPath);
}

(issue imported from #M1114)