diff --git a/puppet/zulip_internal/files/iptables/rules b/puppet/zulip_internal/files/iptables/rules
index 49d22e85c1..235ad1787b 100644
--- a/puppet/zulip_internal/files/iptables/rules
+++ b/puppet/zulip_internal/files/iptables/rules
@@ -17,8 +17,9 @@
 # Accept incoming traffic related to established connections
 -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
 
-# Accept incoming traffic on TCP ports 22 (SSH), 80 (HTTP), 443 (HTTPS), and 5432 (Postgres)
+# Accept incoming traffic on TCP ports 22 (SSH), 25 (SMTP), 80 (HTTP), 443 (HTTPS), and 5432 (Postgres)
 -A INPUT -p tcp --dport   22 -j ACCEPT
+-A INPUT -p tcp --dport   25 -j ACCEPT
 -A INPUT -p tcp --dport   80 -j ACCEPT
 -A INPUT -p tcp --dport  443 -j ACCEPT
 -A INPUT -p tcp --dport 5432 -j ACCEPT