Systems Administrator - Platform Migration & Merge Specialist

Systems Administrator - Platform Migration & Merge Specialist Location: Basingstoke (hybrid) Job Type: Fixed Term Contract (Until 31st March 2027) Salary: £50k - 80k (Pro Rated for period of hire June26-Mar27) Reporting To: The IT Director Key Responsibilities: Google Workspace to M365 and M365 to M365 Migrations Role Overview Reporting to the IT Director, this role provides the technical leadership and hands-on delivery required to continue a multi-phase collaboration platform consolidation programme across the group. The programme is migrating several business units onto a single Microsoft 365 tenant, retiring legacy Google Workspace and standalone Microsoft 365 environments along the way. You will be responsible for overseeing in-flight migrations, planning and executing future migrations, and decommissioning environments that have already been transitioned. The work spans Microsoft 365 tenant-to-tenant migrations, Google Workspace to Microsoft 365 migrations, and the coexistence, cutover and stabilisation activities that surround them. Key Responsibilities Migration Delivery - Take ownership of in-flight and upcoming platform migrations, including both Microsoft 365 to Microsoft 365 (tenant consolidation) and Google Workspace Enterprise to Microsoft 365 transitions. - Design and execute migration approaches for mail, calendars, contacts, files, chat and identity, using the Microsoft Migration Toolset (Exchange Online migration, SharePoint and OneDrive migration tooling) and complementary third-party tooling where appropriate. - Manage coexistence periods where dual systems operate in parallel, including mail flow configuration, calendar interop, free/busy visibility, and delta synchronisation. - Plan and execute cutover activities including domain MX changes, primary SMTP swaps, UPN transitions, and the controlled retirement of source environments. - Write and maintain PowerShell scripts that interact with Exchange Online, Microsoft Graph, Entra ID and SharePoint for bulk operations, validation, reporting and automation. Discovery and Analysis - Develop a thorough understanding of source environments before migration, including users, groups, mail, files, shared drives, calendar resources, chat, third-party integrations and operational workflows. - Use Google Admin tools, GAM, Microsoft Graph, PowerShell, Microsoft Migration Manager and other appropriate tooling to query, analyse and report on source data. - Identify migration risks, edge cases and dependencies, including shared mailboxes, delegations, calendar resource booking, SaaS authentication dependencies, and cross-document references such as Google Sheets IMPORTRANGE. - Document findings and recommend approaches to address them. Identity, Licensing and Coexistence - Plan and implement identity strategies that accommodate Entra ID, Google federation and the broader SaaS application landscape during transitions. - Manage licensing transitions across Microsoft 365 and Google Workspace, including Cloud Identity downgrades for retained identity-only accounts. - Maintain mail flow integrity across domains during coexistence, including accepted domain types, forwarding configurations, primary SMTP and alias management. Tenant Decommissioning - Oversee the controlled decommissioning of source environments after successful migration, covering data retention, identity downgrade, licence release and tenant retirement. - Coordinate retention of legacy native content as a safety net where required. - Manage SaaS application transitions from legacy identity providers to Entra ID single sign-on. Stakeholder Engagement and Proposal Support - Provide the technical analysis and detailed planning required by the IT Director and CTO to build migration proposals for leadership approval. - Communicate progress, risks and decisions through Steering Committee forums. - Translate technical detail for non-technical audiences in user communications, change management materials and service desk guidance. Post-Migration Support - Provide hypercare support during and after migration cutovers. - Engage directly with senior stakeholders and VIP users to triage and resolve complex issues. - Iterate on the support model based on real-world feedback and post-migration metrics. What We're Looking For Essential - Strong administrative expertise in Microsoft Entra ID, Microsoft 365 (Exchange Online, SharePoint Online, OneDrive, Teams) and Google Workspace Enterprise. - Proven experience delivering tenant-to-tenant Microsoft 365 migrations and Google Workspace to Microsoft 365 migrations. - Strong PowerShell skills, including writing scripts that interact with Microsoft Graph, Exchange Online and Entra ID for import, export, validation and automation tasks. - Hands-on experience with the Microsoft Migration Toolset (Exchange Online migration, SharePoint Migration Manager, OneDrive migration) and Google Workspace administration tools including GAM. - Practical understanding of mail flow during migration: accepted domain types, MX cutover, forwarding, primary SMTP and alias strategies, and calendar interop configuration. - Experience decommissioning Google Workspace and Microsoft 365 tenants in a controlled way, including identity-only downgrades to preserve SaaS authentication where needed. - Ability to communicate complex technical concepts to both technical and non-technical stakeholders. - Strong analytical and problem-solving skills, with the patience to work through edge cases methodically. - A proactive, solution-oriented mindset and the ability to manage multiple migration workstreams simultaneously. Desirable - Familiarity with third-party cloud migration tooling such as Movebot, CloudM or BitTitan. - Experience administering Atlassian (Confluence, Jira) and Slack, including merging or consolidating instances. - Experience with Intune and Kandji device management during platform transitions. - Awareness of Microsoft Purview sensitivity labelling and DLP, an