Only suggest, not recommend, an MTA

debian/control

@@ -25,12 +25,11 @@ Depends:
     adduser,
     lsb-base (>= 3.0-10),
     libpam-runtime (>= 1.0.1-11)
-Recommends:
-    exim4 | postfix | mail-transport-agent
 Suggests:
     anacron (>=2.0-1),
     logrotate,
-    checksecurity
+    checksecurity,
+    exim4 | postfix | mail-transport-agent
 Breaks:
     dpkg (<< 1.15.4)
 Provides: cron-daemon