--- courier/imapd-ssl.rc.in.orig	2018-07-29 05:16:41.000000000 +0200
+++ courier/imapd-ssl.rc.in	2020-04-26 13:47:03.472951000 +0200
@@ -31,7 +31,7 @@
 	then
 		rm -f "$TLS_CACHEFILE"
 		touch "$TLS_CACHEFILE"
-		chown @mailuser@ "$TLS_CACHEFILE"
+		/usr/sbin/chown @mailuser@ "$TLS_CACHEFILE"
 		chgrp @mailgroup@  "$TLS_CACHEFILE"
 		chmod 600  "$TLS_CACHEFILE"
 	fi