L3 Support Systems & M365

L3 Support - Systems & M365 (Freelance) - 24 months - Brussels Belgium

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About the Role

We are seeking an elite L3 Support - Systems & M365 Engineer for a freelance mission with our client in Brussels. This is a 24-month high-impact assignment where youll be the escalation point for complex IT incidents driving operational excellence and security across critical infrastructure. Your expertise will directly empower business continuity and innovation ensuring that technology is never a bottleneck for progress.

Why This Role Matters

As the L3 Support - Systems & M365 Engineer you are the backbone of resilient IT operations. Youll solve the toughest challenges escalated from L1/L2 teams safeguard digital assets and enable seamless collaboration for hundreds of users. Your work ensures that our clients infrastructure is robust secure and future-ready making you a key player in their digital transformation journey.

What Youll Be Doing

• Acting as the escalation point for L1/L2 teams resolving complex incidents across Windows environments Microsoft 365 Entra ID Intune and core infrastructure services.
• Diagnosing and resolving advanced issues in Windows Server Active Directory Entra ID DNS DHCP M365 Intune Teams and Exchange Online.
• Performing root cause analysis (RCA) and implementing sustainable corrective actions to prevent recurrence.
• Monitoring infrastructure health using tools such as SolarWinds Microsoft Defender and M365 portals.
• Managing accounts permissions and policies in Active Directory and Entra ID including MFA Conditional Access groups and licenses.
• Administering Microsoft 365 platforms: Exchange Online Teams/Teams Rooms SharePoint and OneDrive.
• Managing and troubleshooting endpoints via Intune including compliance configuration profiles and Autopilot deployments.
• Processing and tracking security alerts from Defender for Endpoint and O365 solutions.
• Maintaining and updating technical documentation operational procedures and best practices.
• Applying and enforcing security and compliance policies (ISO27001 NIS2 GDPR).
• Collaborating with systems and network teams on cross-functional incidents and technical improvements.
• Participating in migrations and infrastructure enhancements under the guidance of the infrastructure team.
• Ensuring all activities comply with GDPR ISO27001 and NIS2 standards.

What Were Looking For

• Ownership mindset: You take initiative drive outcomes and thrive on solving complex problems.
• Proven experience in L3 support roles with a focus on Microsoft ecosystems and enterprise infrastructure.
• Ability to analyze document and communicate technical solutions clearly and effectively.
• Collaborative spirit eager to work alongside high-performing teams and share knowledge.
• Commitment to operational excellence security and continuous improvement.
• Adaptability to evolving technologies and business needs.

Technical Skills

• Windows Server Administration (Intermediate)
• Azure / Entra ID / Conditional Access (Intermediate)
• Network knowledge (Intermediate)
• Defender for Endpoint & 365 (Intermediate)
• DNS & DHCP (Intermediate)
• Technical documentation (Beginner)
• Exchange Online mailflow traces antispam (Intermediate)
• Active Directory management (Intermediate)
• Intune administration Compliance Configuration Profiles (Intermediate)
• ITIL (Nice to have)
• M365 administration (Intermediate)
• Monitoring and incident management (Intermediate)
• Monitoring via SolarWinds (Intermediate)
• Backup and restoration (Nice to have)
• SCCM (Beginner)
• Powershell scripting (Intermediate)
• Segregation and security (Beginner)
• Teams Administration - TeamsRoom (Intermediate)
• Virtualization (VMware Hyper-V) (Nice to have)

Language Proficiency

• Professional proficiency in English required.
• Knowledge of French or Dutch is a plus.

Other Requirements

• Freelance position: 24-month mission partial on-site presence in Brussels required (minimum 3 days per week).
• Compliance with GDPR ISO27001 NIS2 and clients Code of Conduct for External Service Providers.
• Ability to plan leave in coordination with the Senior Officer and ensure service continuity.
• Adherence to standard office hours (Monday to Friday 7:00 AM to 7:00 PM) unless otherwise authorized.
• Project may be renewed up to a maximum of 880 working days.

Ready to Build the Future

If youre ready to join the top 2% of builders and make a real impact upload your CV now and become part of the RELYzIT Talent movement. For any questions contact Henri Couchard MSP Consultant at

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