M365 Architect - Exchange/Messaging

In this role you will own the messaging architecture for a major technology transformation programme, designing a secure, resilient environment and guiding the migration to Microsoft 365. You will assess current Exchange and Microsoft 365 estates, plan coexistence and target-state architecture, and define mail flow, DNS, and recipient strategies. You will shape migration patterns, sequencing, and end-user experience while ensuring security, compliance and data integrity. This is a senior, architecture-focused position that partners with security, identity, and application teams to deliver a scalable messaging platform.

• Autonomy to develop and grow skills
• Exciting project work making a difference in society
• Flexible working including home working
• 25 days annual leave plus bank holidays
• Pension salary-exchange with employer contributions
• Private medical insurance (non-contributory)

• Assess current Exchange and Microsoft 365 estate including configuration, tenants, domains, mail flow and dependencies
• Define coexistence and target-state messaging architectures across tenants and environments
• Establish migration patterns, sequencing, pilots, production waves and post-migration support
• Design secure, resilient mail-routing, DNS, Autodiscover, and recipient management
• Define governance for retention, compliance, eDiscovery and information governance
• Provide architectural assurance and guidance during migration, cutover and early-life support
• Produce and maintain HLDs/LLDs, diagrams, standards and decision records
• Coordinate with cross-functional teams (identity, security, applications, network) to manage messaging dependencies

• Extensive experience with Exchange Online, Microsoft 365 and enterprise messaging environments
• Hybrid and/or multi-tenant messaging architecture design
• Experience with tenant-to-tenant mailbox migrations and complex coexistence
• Expert knowledge of mail routing, connectors, domains, transport rules and recipient management
• Strong DNS/MX/Autodiscover knowledge and service discovery
• Experience with Defender for Office 365 and information governance concepts
• Strong documentation and architectural design skills (HLDs, LLDs)
• Excellent stakeholder-management and communication skills

• Stakeholder-management
• Communication of complex technical decisions to non-technical audiences
• Problem solving and analytical thinking
• Exchange Online
• Microsoft 365
• Hybrid/multi-tenant architectures