diff --git a/example.env b/example.env
index 4cb50ab..d620536 100644
--- a/example.env
+++ b/example.env
@@ -5,9 +5,6 @@ CONTAINER_PREFIX=
 # The hostname to use for the local SMTP server
 LOCAL_SMTP_HOST=smtp
 
-# The port to use for the local SMTP server
-LOCAL_SMTP_PORT=2500
-
 # The username for authenticating to the local SMTP server
 LOCAL_SMTP_USER=smtp
 
@@ -57,10 +54,3 @@ ETHERPAD_NODE_ENV=production
 
 # The admin password for the Etherpad instance
 ETHERPAD_ADMIN_PASSWORD=
-
-# The ports on which to run apps
-# See also: LOCAL_SMTP_PORT
-ETHERPAD_PORT=9001
-HTTP_PORT=8080
-GEMINI_PORT=1965
-VAULTWARDEN_PORT=9000
diff --git a/make/container.mk b/make/container.mk
index a9758ff..ba398a7 100644
--- a/make/container.mk
+++ b/make/container.mk
@@ -1,8 +1,14 @@
+capitalise = $(shell _v="$(1)"; echo $${_v^^})
+
 CPU_ARCH := $(if $(shell which arch 2>/dev/null),\
 	$(shell arch),\
 	$(shell lscpu | grep ^Architecture: | sed "s/^Architecture:[[:space:]]*\([[:alnum:][:punct:]]\+\).*/\1/"))
 IMAGE_PREFIX := $(if $(filter armv7%,$(CPU_ARCH)),armv7/)
-COMPOSE_CMD := IMAGE_PREFIX="$(IMAGE_PREFIX)" podman-compose
+COMPOSE_CMD := \
+	IMAGE_PREFIX="$(IMAGE_PREFIX)" \
+	LOCAL_SMTP_PORT=$(PORT_smtp) \
+	$(foreach module,$(ALL_MODULES),$(call capitalise,$(module))_PORT=$(PORT_$(module))) \
+	podman-compose
 REGISTRY_DOMAIN := git.joeac.net
 REGISTRY_USER := joeac
 
diff --git a/make/vars.mk b/make/vars.mk
index f7ec98d..9f7a701 100644
--- a/make/vars.mk
+++ b/make/vars.mk
@@ -2,6 +2,11 @@ SUBDOMAIN_http := @
 SUBDOMAIN_vaultwarden := pwd
 SUBDOMAIN_etherpad := docs
 SUBDOMAIN_ln := ln
+PORT_etherpad := 9001
+PORT_http := 8080
+PORT_gemini := 1965
+PORT_smtp := 2500
+PORT_vaultwarden := 9000
 HOSTNAME := $(shell cat /etc/hostname)
 HOSTNAMES := pi-broughton blade-canongate
 MODULES_pi-broughton := http gemini smtp vaultwarden ln