diff --git a/pmg-planning-deployment.adoc b/pmg-planning-deployment.adoc
index 9c81069..73bca8a 100644
--- a/pmg-planning-deployment.adoc
+++ b/pmg-planning-deployment.adoc
@@ -129,6 +129,9 @@ Recommended System Requirements
 ** for use in a virtual machine, activate Intel VT/AMD-V CPU flag
 
 * 4 GiB RAM
++
+Memory requirements can increase significantly with heavy email traffic, many
+filter rules, enabling additional signatures or third-party tools.
 
 * Bootable CD-ROM-drive or USB boot support