Don't fallback to Plaintext per default for legacy class

lib/public/util.php

@@ -65,26 +65,35 @@ class Util {
 	 * @param string $bcc
 	 * @deprecated Use \OCP\Mail\IMailer instead
 	 */
-	public static function sendMail( $toaddress, $toname, $subject, $mailtext, $fromaddress, $fromname,
+	public static function sendMail($toaddress, $toname, $subject, $mailtext, $fromaddress, $fromname,
 		$html = 0, $altbody = '', $ccaddress = '', $ccname = '', $bcc = '') {
 		$mailer = \OC::$server->getMailer();
 		$message = $mailer->createMessage();
-		$message->setTo(array($toaddress => $toname));
+		$message->setTo([$toaddress => $toname]);
 		$message->setSubject($subject);
 		$message->setPlainBody($mailtext);
-		$message->setFrom(array($fromaddress => $fromname));
+		$message->setFrom([$fromaddress => $fromname]);
 		if($html === 1) {
 			$message->setHTMLBody($altbody);
 		}
+
+		if($altbody === '') {
+			$message->setHTMLBody($mailtext);
+			$message->setPlainBody('');
+		} else {
+			$message->setHtmlBody($mailtext);
+			$message->setPlainBody($altbody);
+		}
+
 		if(!empty($ccaddress)) {
 			if(!empty($ccname)) {
-				$message->setCc(array($ccaddress => $ccname));
+				$message->setCc([$ccaddress => $ccname]);
 			} else {
-				$message->setCc(array($ccaddress));
+				$message->setCc([$ccaddress]);
 			}
 		}
 		if(!empty($bcc)) {
-			$message->setBcc(array($bcc));
+			$message->setBcc([$bcc]);
 		}
 
 		$mailer->send($message);