adminerevo/editor/include/editing.inc.php

<?php
/** Encode e-mail header in UTF-8
* @param string
* @return string
*/
function email_header($header) {
	// iconv_mime_encode requires PHP 5, imap_8bit requires IMAP extension
	return "=?UTF-8?B?" . base64_encode($header) . "?="; //! split long lines
}

/** Send e-mail in UTF-8
* @param string
* @param string
* @param string
* @param string
* @param array
* @return 
*/
function send_mail($email, $subject, $message, $from = "", $files = array("error" => array())) {
	$eol = (strncasecmp(PHP_OS, "win", 3) ? "\n" : "\r\n"); // PHP_EOL available since PHP 4.3.10 and 5.0.2
	$message = str_replace("\n", $eol, wordwrap(str_replace("\r", "", "$message\n")));
	$boundary = uniqid("boundary");
	$attachments = "";
	foreach ($files["error"] as $key => $val) {
		if (!$val) {
			$attachments .= "--$boundary$eol"
				. "Content-Type: " . str_replace("\n", "", $files["type"][$key]) . $eol
				. "Content-Disposition: attachment; filename=\"" . preg_replace('~["\\n]~', '', $files["name"][$key]) . "\"$eol"
				. "Content-Transfer-Encoding: base64$eol$eol"
				. chunk_split(base64_encode(file_get_contents($files["tmp_name"][$key])), 76, $eol) . $eol
			;
		}
	}
	$beginning = "";
	$headers = "Content-Type: text/plain; charset=utf-8$eol" . "Content-Transfer-Encoding: 8bit";
	if ($attachments) {
		$attachments .= "--$boundary--$eol";
		$beginning = "--$boundary$eol$headers$eol$eol";
		$headers = "Content-Type: multipart/mixed; boundary=\"$boundary\"";
	}
	$headers .= $eol . "MIME-Version: 1.0$eol" . "X-Mailer: Adminer Editor"
		. ($from ? $eol . "From: " . str_replace("\n", "", $from) : "") //! should escape display name
	;
	return mail($email, email_header($subject), $beginning . $message . $attachments, $headers);
}