Sakib Mahmud | System Administrator

Approach

The SysAdmin Philosophy

The framework I apply to every infrastructure I touch - anticipate, protect, and optimize.

Proactive Monitoring

Catch resource spikes and anomalies before they impact end-users. Downtime costs more than prevention.

Security by Design

Strict firewall rules, VLAN segmentation, encrypted VPN tunnels, and enforced SSL/SSH - security from day one.

Disaster Recovery

Hardware fails, businesses shouldn't. Automated backups and redundant configs mean recovery is swift and absolute.

Expertise

What I Specialize In

End-to-end technical domains - from server rooms to cloud consoles.

Server & OS Administration

Linux & Windows · On-prem & Cloud

Server Migration Server Monitoring Server Management Server Optimization Security Hardening Backup & Recovery Container Deployment 3CX Call Center Installation

Network Engineering

Design · Secure · Optimize

Network Design & Architecture Firewall Management VPN Deployment VLAN Segmentation BGP Routing Bandwidth Optimization Network Monitoring Traffic Shaping

Cloud & Web Hosting

Deploy · Scale · Maintain

Cloud Infrastructure Setup Web Hosting Management Cloud Migration CDN Configuration Database Administration SSL & Domain Management Load Balancing Cost Optimization

Enterprise Communications

Email · VOIP · Workspace

Business Email Setup Anti-Spam Configuration VOIP & Call Center Setup Workspace Administration Remote Work Infrastructure Mail Server Deployment Unified Communications Business Continuity

Work

Major Projects

A selection of high-impact engagements across enterprise VoIP, hosting infrastructure, email deliverability, and secure networking.

Enterprise VoIP & Call Center - 200 Seats

Wilmington, DE

Deployed and maintained a full-scale 3CX-based call center for a remote sales operation with 200 concurrent seats. Led end-to-end implementation including SIP trunk provisioning, number porting, carrier integration, IVR design, WebRTC configuration, and ongoing system maintenance, security patching, and performance optimization.

3CX PBX Installation SIP Trunking DID Provisioning Number Porting Amazon Chime SDK Twilio SIP Telnyx Bandwidth.com WebRTC Gateway STUN/TURN Setup IVR & Call Flow Design Ring Groups & Queues Extension Management Hot-Desking QoS Configuration CDR Reporting CRM Integration Voicemail & Auto-Attendant Failover & Redundancy Security Patching SMS/MMS Integration

+ Firewall rules for SIP, call recording, real-time monitoring, and carrier failover management

Large-Scale Web Hosting Infrastructure

Miami, FL

Managed the full hosting stack for a high-volume web hosting company - from dedicated server provisioning and cPanel/WHM administration to email server tuning, database optimization, security hardening, and custom automation scripting across hundreds of client accounts.

cPanel / WHM Administration Dedicated Server Management CloudLinux & CageFS LiteSpeed / Apache Tuning WordPress Management Custom App Hosting Exim / Postfix Mail Servers SpamAssassin & RBL SPF / DKIM / DMARC SSL Automation (Let's Encrypt) MySQL / MariaDB Optimization DNS Zone Management CSF / Fail2Ban Firewall ModSecurity WAF DDoS Mitigation JetBackup / R1Soft Cloudflare CDN Server Migration RAID Monitoring Custom Bash Scripting OS Patching & Kernel Updates Resource Limit Tuning WHMCS Integration

+ Load balancing, and client account migrations

Email & SMS Marketing Infrastructure

Wilmington, DE

Built and maintained a dedicated high-volume email and SMS blast platform for a marketing-driven sales organization. Managed sender reputation, deliverability pipelines, compliance, and CRM integration to drive measurable lead generation outcomes for the sales team.

Dedicated Email Server Setup PowerMTA / Postfix Config Dedicated IP Warming IP Pool Management SPF / DKIM / DMARC Alignment DMARC Reporting Sender Reputation Monitoring Bounce Handling & Suppression Lists Feedback Loop (FBL) Setup Blacklist Monitoring & Removal SMS Blast Infrastructure Twilio / Bandwidth SMS API A2P 10DLC Registration Toll-Free Verification SMS Number Reputation Email List Hygiene & Validation Delivery Rate Optimization CRM Integration Lead Pipeline Automation Domain Rotation Strategy

+ Inbox placement testing and campaign performance analysis

Secure Office Network & Remote Workspace

Houston, TX

Designed and deployed a secure, zero-trust office network with hardened perimeter defenses, remote workforce connectivity, and centralized identity management. Implemented SD-WAN-ready architecture, full VLAN segmentation, and overlay networking to support a geographically distributed team.

Custom Firewall Rules VLAN Segmentation Inter-VLAN Routing Site-to-Site VPN (IPSec / WireGuard) ZeroTier Overlay Network Tailscale Mesh VPN Zero-Trust Architecture SSO Implementation RADIUS Authentication Active Directory / LDAP MFA Enforcement Certificate-Based Auth Remote Desktop Infrastructure MDM Policies Guest Network Isolation Bandwidth QoS DHCP & DNS Server Endpoint Security Policies Network Documentation

+ Remote onboarding workflows and endpoint compliance

Contact

Let's Connect

Open to new projects, collaborations, and infrastructure challenges.