--- a/dovecot.service.in
+++ b/dovecot.service.in
@@ -7,6 +7,7 @@
 ExecStartPre=/usr/libexec/dovecot/prestartscript
 ExecStart=@sbindir@/dovecot -F
 ExecReload=/bin/kill -HUP $MAINPID
+PrivateTmp=true
 NonBlocking=yes
 
 [Install]