-# optimization, this only needs to run once.
-if ! openssl x509 -checkend $(( 60 * 60 * 24 * 3 )) -noout -in /etc/exim4/fullchain.pem; then
+# optimization, this only needs to run once. But, if we move to a
+# computer we haven't used much, we need to fetch a fresh cert.
+# Existence check is just to avoid ugly error message from openssl.
+if [[ ! -e /etc/exim4/fullchain.pem ]] || ! openssl x509 -checkend $(( 60 * 60 * 24 * 3 )) -noout -in /etc/exim4/fullchain.pem; then