Mail Services

How to Configure Postfix Mail Server on Debian 13 — step-by-step Debian 13 tutorial on Progressive Robot

How to Configure Postfix Mail Server on Debian 13

Introduction Debian 13 Trixie is built around the ethos of stability and free software. Setting up configure postfix mail server on Trixie leverages the same proven Debian packaging system that powers millions of servers worldwide, while benefiting from the latest upstream releases included in the Trixie freeze. Follow each step carefully and the resulting configuration […]

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How to Configure OpenDKIM with Postfix on RHEL 10 — step-by-step RHEL 10 tutorial on Progressive Robot

How to Configure OpenDKIM with Postfix on RHEL 10

Introduction RHEL 10 ships with a stable, security-hardened base that makes deploying configure opendkim with postfix both straightforward and auditable. This tutorial covers the complete procedure for how to Configure OpenDKIM with Postfix on RHEL 10, including dnf module streams where applicable, systemd unit management, and the firewalld rules required for network-facing services. Prerequisites The […]

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Common Problems 119612

Debian 13 – Postfix Queue Deferred by DNS Resolution Errors – Mail Flow Repair

🟠 High   ⏱ 5–30 min  Last verified: 16 August 2025 Affected versions: Debian 13 (Trixie) 📖 ~1 min read Table of contents Symptom & Impact Environment & Reproduction Root Cause Analysis Quick Triage Step-by-Step Diagnosis Solution – Primary Fix Solution – Alternative Approaches Verification & Acceptance Criteria Rollback Plan Prevention & Hardening Related Errors […]

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Common Problems 111074

Windows Server 2025 — SMTP relay port 25 blocked by another service — Fix & Prevention

🟠 High   ⏱ 5–30 min  Last verified: 12 August 2025 Affected versions: Windows Server 2025 📖 ~2 min read Table of contents Symptom & Impact Environment & Reproduction Root Cause Analysis Quick Triage Step-by-Step Diagnosis Solution — Primary Fix Solution — Alternative Approaches Verification & Acceptance Criteria Rollback Plan Prevention & Hardening Related Errors […]

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How to Set Up Mail Relay with Postfix on RHEL 10 — step-by-step RHEL 10 tutorial on Progressive Robot

How to Set Up Mail Relay with Postfix on RHEL 10

Introduction Setting up set up mail relay with postfix on a RHEL 10 server is a common task for system administrators, DevOps engineers, and site reliability engineers. This guide explains how to Set Up Mail Relay with Postfix on RHEL 10, with all the commands you need, the SELinux and firewalld considerations to keep in […]

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How to Install and Configure Dovecot IMAP Server on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Install and Configure Dovecot IMAP Server on RHEL 9

Dovecot is a fast, secure, and easy-to-configure IMAP and POP3 server that works seamlessly alongside Postfix on RHEL 9. Once Postfix is delivering incoming mail to a user’s Maildir, Dovecot allows mail clients such as Thunderbird or Outlook to retrieve those messages over IMAP or POP3 — with optional SSL/TLS encryption for both protocols. This […]

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How to Configure a Static IP Address with Netplan on Ubuntu 24.04 — step-by-step Linux tutorial on Progressive Robot

How to Configure DKIM, SPF and DMARC on Ubuntu 24.04

DKIM, SPF, and DMARC are email authentication standards that prevent spoofing and improve email deliverability. This guide configures all three on a Postfix server on Ubuntu 24.04 LTS. Tested and valid on: Ubuntu 24.04 LTS Prerequisites Ubuntu 24.04 LTS server Postfix installed and running Access to your domain DNS records A user with sudo privileges […]

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Common Problems 114078

RHEL 10 Postfix Cannot Send Outbound Mail Due to DNS and Firewall Issues

🟠 High   ⏱ 5–30 min  Last verified: 25 July 2025 Affected versions: RHEL 10 📖 ~1 min read Table of contents Symptom & Impact Environment & Reproduction Root Cause Analysis Quick Triage Step-by-Step Diagnosis Solution — Primary Fix Solution — Alternative Approaches Verification & Acceptance Criteria Rollback Plan Prevention & Hardening Related Errors & […]

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How to Install and Configure AIDE on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Install and Configure AIDE on RHEL 9

AIDE (Advanced Intrusion Detection Environment) is an open-source file integrity monitoring tool that detects unauthorized changes to files on a Linux system. It creates a cryptographic baseline database of your file system and compares the current state against that baseline on every check, alerting you to any additions, deletions, or modifications. AIDE is recommended by […]

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How to Configure a Static IP Address with Netplan on Ubuntu 24.04 — step-by-step Linux tutorial on Progressive Robot

How to Install and Configure Postfix Mail Server on Ubuntu 24.04

Postfix is a popular, high-performance Mail Transfer Agent (MTA) that routes and delivers email. This guide installs and configures Postfix as an outgoing SMTP server on Ubuntu 24.04 LTS. Tested and valid on: Ubuntu 24.04 LTS Prerequisites Ubuntu 24.04 LTS server A registered domain name DNS MX records pointing to your server A user with […]

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