diff -up dovecot-2.3.2/dovecot.service.in.systemd_w_protectsystem dovecot-2.3.2/dovecot.service.in
--- dovecot-2.3.2/dovecot.service.in.systemd_w_protectsystem 2018-07-09 12:00:13.359193526 +0200
+++ dovecot-2.3.2/dovecot.service.in 2018-07-09 12:00:46.387716884 +0200
@@ -23,6 +23,7 @@ ExecReload=@bindir@/doveadm reload
ExecStop=@bindir@/doveadm stop
PrivateTmp=true
NonBlocking=yes
+# this will make /usr /boot /etc read only for dovecot
ProtectSystem=full
ProtectHome=no
PrivateDevices=true