Systems Administrator - Platform Migration & Merge Specialist

Systems Administrator - Platform Migration & Merge Specialist

Salary: £50k - 80k (Pro Rated for period of hire Aug
26-Mar
27)

Reporting To: The IT Director

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.

• 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 One Drive 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 Power Shell scripts that interact with Exchange Online, Microsoft Graph, Entra  SharePoint for bulk operations, validation, reporting and automation.

• 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, Power Shell, 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.

• Plan and implement identity strategies that accommodate Entra , 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.

• 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 e sign-on.

• 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.

• 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.

• Strong administrative expertise in Microsoft Entra , Microsoft 365 (Exchange Online, SharePoint Online, One Drive, Teams) and Google Workspace Enterprise.
• Proven experience delivering tenant-to-tenant Microsoft 365 migrations and Google Workspace to Microsoft 365 migrations.
• Strong Power Shell skills, including writing scripts that interact with Microsoft Graph, Exchange Online and Entra  import, export, validation and automation tasks.
• Hands-on experience with the Microsoft Migration Toolset (Exchange Online migration, SharePoint Migration Manager, One Drive 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…