diff --git a/setup/mail-postfix.sh b/setup/mail-postfix.sh
index 10322bc..11a2b30 100755
--- a/setup/mail-postfix.sh
+++ b/setup/mail-postfix.sh
@@ -41,13 +41,6 @@ source /etc/mailinabox.conf # load global vars
 #   always will.
 # * `ca-certificates`: A trust store used to squelch postfix warnings about
 #   untrusted opportunistically-encrypted connections.
-#
-# postgrey is going to come in via the Mail-in-a-Box PPA, which publishes
-# a modified version of postgrey that lets senders whitelisted by dnswl.org
-# pass through without being greylisted. So please note [dnswl's license terms](https://www.dnswl.org/?page_id=9):
-# > Every user with more than 100’000 queries per day on the public nameserver
-# > infrastructure and every commercial vendor of dnswl.org data (eg through
-# > anti-spam solutions) must register with dnswl.org and purchase a subscription.
 echo "Installing Postfix (SMTP server)..."
 apt_install postfix postfix-sqlite postfix-pcre postgrey ca-certificates
 
diff --git a/setup/start.sh b/setup/start.sh
index 9d64bba..671f444 100755
--- a/setup/start.sh
+++ b/setup/start.sh
@@ -4,7 +4,7 @@
 
 source setup/functions.sh # load our functions
 
-# Check system setup: Are we running as root on Ubuntu 14.04 on a
+# Check system setup: Are we running as root on Ubuntu 18.04 on a
 # machine with enough memory? Is /tmp mounted with exec.
 # If not, this shows an error and exits.
 source setup/preflight.sh
diff --git a/setup/system.sh b/setup/system.sh
index 29ee97b..32cf998 100755
--- a/setup/system.sh
+++ b/setup/system.sh
@@ -134,8 +134,8 @@ hide_output apt-get update
 fi
 
 # ### Suppress Upgrade Prompts
-# Since Mail-in-a-Box might jump straight to 18.04 LTS, there's no need
-# to be reminded about 16.04 on every login.
+# When Ubuntu 20 comes out, we don't want users to be prompted to upgrade,
+# because we don't yet support it.
 if [ -f /etc/update-manager/release-upgrades ]; then
 	tools/editconf.py /etc/update-manager/release-upgrades Prompt=never
 	rm -f /var/lib/ubuntu-release-upgrader/release-upgrade-available
@@ -182,7 +182,6 @@ fi
 # * DNSSEC signing keys (see `dns.sh`)
 # * our management server's API key (via Python's os.urandom method)
 # * Roundcube's SECRET_KEY (`webmail.sh`)
-# * ownCloud's administrator account password (`owncloud.sh`)
 #
 # Why /dev/urandom? It's the same as /dev/random, except that it doesn't wait
 # for a constant new stream of entropy. In practice, we only need a little
diff --git a/setup/web.sh b/setup/web.sh
index 021a9b7..7f9b163 100755
--- a/setup/web.sh
+++ b/setup/web.sh
@@ -21,7 +21,7 @@ echo "Installing Nginx (web server)..."
 
 apt_install nginx php7.0-cli php7.0-fpm
 
-# Set PHP7 as the default
+# Set PHP7.0 as the default since several versions are available.
 update-alternatives --set php /usr/bin/php7.0
 
 rm -f /etc/nginx/sites-enabled/default