Senior Microsoft Infrastructure & Exchange Engineer

Own the health, security, and continuity of the organisation's core Microsoft platform:
Exchange Server 2019 (on-premises) in hybrid with Microsoft 365, Active Directory, Group Policy, DNS/DHCP, and the identity and email-security layers that sit on top of them. The role helps maintain reliable corporate messaging, mailbox availability, and identity services in a multi-site business environment.

• Install, configure, administer, and upgrade Microsoft Exchange Server 2019 on-premises; apply cumulative updates and security patches on a controlled schedule.
• Run and maintain Exchange Hybrid with Microsoft 365: hybrid configuration, free/busy, cross-premises mail flow, and directory synchronisation health.
• Execute mailbox migrations (on-prem to/from Exchange Online) with zero-data-loss cutovers and a tested rollback for each wave.
• Manage mailbox lifecycle, distribution and shared mailboxes, mail flow, transport rules, send/receive connectors, and certificate lifecycle (issuance, renewal, binding) with no lapsed-certificate outages.
• Design, build, and maintain Database Availability Groups (DAG) for Exchange high availability; own failover testing and quorum health.
• Diagnose and resolve complex mail-delivery, queue, performance, and availability problems using message tracking, protocol logs, and transport diagnostics.

• Perform advanced Active Directory administration: domain services, sites, trusts, OU design, delegation, user authentication, and permissions.
• Design, implement, troubleshoot, and optimise Group Policy (GPO): scope, precedence, security filtering, and drift control.
• Administer and maintain DNS and DHCP as authoritative infrastructure services for the estate.
• Own AD replication health, security hardening (privileged accounts, tiering), and disaster-recovery readiness for the directory (backup, forest/domain recovery runbook, tested restore).

• Administer the enterprise email-security gateway/solution: anti-spam, anti-phishing, malware protection, content filtering, quarantine management, and policy tuning.
• Own the sender-authentication stack (SPF, DKIM, and DMARC) from monitoring through enforcement, and manage mail routing and inbound/outbound threat protection.
• Investigate email-borne threats and phishing incidents with Information Security; tune policies to cut false positives without opening exposure.

• Apply working command of TCP/IP, DNS, routing, switching, firewalls, VPNs, VLANs, and NAT to keep messaging and identity reachable and secure.
• Troubleshoot network-layer faults affecting mail flow, hybrid connectivity, and authentication end to end.
• Apply network-security principles and integrate cleanly across messaging, identity, cloud, and the security stack.

• Administer Microsoft 365, Entra  (Azure AD), and Single Sign-On (SSO): tenant configuration, conditional access, and application registrations in coordination with Information Security.
• Build and maintain Power Shell scripting and automation for provisioning, reporting, bulk operations, and repeatable runbooks.
• Own monitoring, backup, disaster recovery, patching, and infrastructure documentation for the messaging and identity estate; keep runbooks and topology current.

• Provide senior-level escalation for messaging, identity, and email-security incidents raised by IT Team Leaders and the Service Desk.
• Maintain up-to-date, formally registered technical documentation, standard operating procedures, and as-built diagrams.
• Contribute to departmental KPI objectives set for the financial year.
• Ensure IT policies, security standards, and…