diff --git a/Dockerfile b/Dockerfile
index 5395bf5..054545a 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -14,5 +14,8 @@ RUN apt-get -y install supervisor postfix sasl2-bin opendkim opendkim-tools
 # Add files
 ADD assets/install.sh /opt/install.sh
 
+# Expose port
+EXPOSE 25
+
 # Run
 CMD /opt/install.sh;/usr/bin/supervisord -c /etc/supervisor/supervisord.conf