2 posts tagged with "firewall"

Published on September 4, 2026

A firewall should allow the traffic your server needs and quietly refuse the rest. To configure VPS firewall rules safely, start with the services that must remain reachable, especially SSH, then add web and application ports one at a time. Do not begin by blocking everything from the only terminal session you have open. That is how a calm maintenance task becomes a console-recovery task.

For most Linux VPS deployments, the practical goal is simple: deny unsolicited inbound traffic by default, allow required outbound traffic, and create narrow inbound rules for trusted users and services. This reduces attack surface without making routine administration difficult.

Reliable email delivery to the recipient depends not only on the mail server itself, but also on correct DNS records and firewall configuration. If something is wrong with those, your messages are very likely to land in the Spam folder - or not be delivered at all.

This article outlines the key steps that will allow you to achieve nearly 100% reliable delivery of messages sent from your server. In Part 1, we will walk through the possible firewall-related issues in detail; in Part 2, you will find instructions for configuring DNS records.

The information in this article applies only to mail servers running on Linux distributions. Debian 12 and Rocky Linux 8.10 with the FASTPANEL control panel are used as examples.