diff --git a/CHANGELOG.md b/CHANGELOG.md
index d450cf9..81dedc8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,6 +20,7 @@ Control panel:
 
 Other:
 
+* Set systemd journald log retention to 10 days (from no limit) to reduce disk usage.
 * Fixed log processing for submission lines that have a sasl_sender or other extra information.
 
 Version 55 (October 18, 2021)
diff --git a/setup/system.sh b/setup/system.sh
index ed399ba..036fe3f 100755
--- a/setup/system.sh
+++ b/setup/system.sh
@@ -75,6 +75,13 @@ then
 	fi
 fi
 
+# ### Set log retention policy.
+
+# Set the systemd journal log retention from infinite to 10 days,
+# since over time the logs take up a large amount of space.
+# (See https://discourse.mailinabox.email/t/journalctl-reclaim-space-on-small-mailinabox/6728/11.)
+tools/editconf.py /etc/systemd/journald.conf MaxRetentionSec=10day
+
 # ### Add PPAs.
 
 # We install some non-standard Ubuntu packages maintained by other