Avoid potential issue with overlong lines in Emails

diff --git a/wcfsetup/install/files/lib/system/email/Email.class.php b/wcfsetup/install/files/lib/system/email/Email.class.php
index 4b50aa39bca6deab8ea33840354fa23fca3352c2..795139243a2b632d32f30703a8014b156459b1c1 100644 (file)
--- a/wcfsetup/install/files/lib/system/email/Email.class.php
+++ b/wcfsetup/install/files/lib/system/email/Email.class.php
@@ -389,10 +389,10 @@ class Email {
                $headers[] = ['date', $this->getDate()->format(\DateTime::RFC2822)];
                $headers[] = ['message-id', $this->getMessageID()];
                if ($this->getReferences()) {
-                       $headers[] = ['references', implode(' ', $this->getReferences())];
+                       $headers[] = ['references', implode("\r\n   ", $this->getReferences())];
                }
                if ($this->getInReplyTo()) {
-                       $headers[] = ['in-reply-to', implode(' ', $this->getInReplyTo())];
+                       $headers[] = ['in-reply-to', implode("\r\n   ", $this->getInReplyTo())];
                }
                $headers[] = ['mime-version', '1.0'];