Complete migration of 5 mailboxes from Google Workspace to Microsoft 365 with full DNS configuration, zero downtime, and 100% data integrity. Configured all required DNS records including CNAME, TXT (SPF), SRV, and MX records in Wix DNS for seamless email routing and autodiscovery.
Technologies Used
Deployed and configured OPNsense firewall with dual ISP setup — 1 public IP and 1 private IP. Implemented automatic failover for high availability, traffic load balancing for optimal performance, and WireGuard VPN for secure remote access. Complete network security hardening with custom firewall rules, NAT configuration, and traffic shaping.
Technologies Used
Designed and deployed a hybrid mail relay architecture to bypass ISP-level blocking of outbound TCP/25, using an AWS EC2 (Ubuntu) instance running Postfix as a relay, connected to an on-prem Exchange Server via a WireGuard VPN tunnel through OPNsense. Configured inbound mail routing from the internet to Exchange over the VPN, and outbound relay from Exchange through Postfix to Brevo SMTP with authenticated relay and TLS. Diagnosed and resolved Postfix "Relay access denied" errors, WireGuard routing issues, and OPNsense firewall rules blocking VPN traffic.
Technologies Used
Documentation
Hardened a production Exchange Server 2019 environment in response to an active phishing campaign impersonating a government tax authority. Enabled and tuned the built-in Anti-Spam Agent suite (Content Filter, Sender Filter, Recipient Filter, Sender ID, Protocol Analysis), set the SCL reject threshold to 7, enforced Sender ID spoofed-domain rejection, and added the Spamhaus ZEN blocklist. Built custom Transport Rules to block a known malicious sender domain and to quarantine dangerous attachment types (.exe, .js, .vbs, .bat, .ps1, .iso, and more). Enabled SMTP protocol logging for ongoing forensic visibility.
Technologies Used
Built and self-hosted this website (quantumitservices.co.in) on a personal, on-premises virtualization stack rather than commercial hosting. Deployed a Proxmox VE hypervisor to run virtual machines, including a Red Hat Enterprise Linux VM configured as the web server for this site, and a separate Windows Server VM (DC01) running Active Directory Domain Services to manage the wider home-lab network. Handled web server setup, PHP mail integration (PHPMailer/SMTP), VM resource allocation, and network segmentation between the Linux and Windows environments.