diff --git a/mox-/config.go b/mox-/config.go
index 5e36efc..3bc9d78 100644
--- a/mox-/config.go
+++ b/mox-/config.go
@@ -1617,6 +1617,7 @@ func prepareDynamicConfig(ctx context.Context, log mlog.Log, dynamicPath string,
 		}
 	}
 
+	c.MonitorDNSBLZones = nil
 	for _, s := range c.MonitorDNSBLs {
 		d, err := dns.ParseDomain(s)
 		if err != nil {