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Practical field notes for teams diagnosing email deliverability, DNS authentication, sender reputation, Linux, MTA, cloud, monitoring, and DevOps failures.

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Technical knowledge system connecting email identity, secure mail flow, servers, cloud operations, monitoring, and runbooks

182 Published articles

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Articles on email deliverability, DNS, Linux, MTA operations, DevOps, monitoring, and incident recovery.

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Short, practical guidance for teams that need to diagnose, repair, and run production email systems.

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Client traffic enters one floating virtual IP owned by an active Linux IPVS director, while a synchronized standby director and health checks protect multiple real servers

Linux, MTA & Security · Jun 3, 2021 · 24 min read

Linux Virtual Server High Availability with IPVS and Keepalived

Build and operate a two-director Linux Virtual Server with IPVS, Keepalived VRRP, backend health checks, NAT or Direct Routing, state synchronization, failover testing, and rollback.

Layered application traffic becomes Ethernet frames, crosses a switch and router between subnets, and connects wired, wireless, VLAN, IPv4, IPv6 and NAT concepts

Linux, MTA & Security · May 14, 2021 · 85 min read

Networking Basics: Ethernet, IP, Routing, Switching, VLANs, IPv6 and NAT

Comprehensive networking notes covering Ethernet, CSMA/CD, MAC and ARP, IP flow, switching, routing, OSI, subnetting, RIP, EIGRP, OSPF, wireless, VLANs, Frame Relay, IPv6 and NAT.

A Linux server security workflow moves from inventory and surface discovery through configuration review, risk ranking, controlled hardening, verification, centralized audit logging, and rollback

Linux, MTA & Security · Dec 10, 2020 · 25 min read

Linux Security Audit and Hardening: Production Guide

Audit and harden Linux through evidence collection, service and identity review, SSH, patching, auditd, permissions, SELinux or AppArmor, firewall controls, verification, and rollback.