M365 Architect – Exchange/Messaging

Jobtailor; Greater London; On-site; GBP 90,000 - 125,000; Full time

Job summary

Jobtailor is seeking an experienced Messaging Architect to own the end-to-end messaging architecture during a Microsoft 365 transformation. You will lead technical delivery across Exchange Online, hybrid and multi-tenant environments, defining migration patterns, mail routing, DNS, security controls and governance alignment.

The role requires strong architectural judgement, stakeholder management and the ability to resolve complex cross-boundary issues while ensuring continuity during cutover

Qualifications

• Extensive architecture experience across Exchange Online, Microsoft 365 and enterprise messaging environments.
• Proven experience designing hybrid and/or multi-tenant messaging architectures.
• Strong experience delivering tenant-to-tenant mailbox migrations and complex coexistence arrangements.

Responsibilities

• Own the messaging architecture and provide technical leadership across the transformation lifecycle.
• Assess the current Exchange and Microsoft 365 estate, including tenants, domains, mail flow, recipients, dependencies, integrations and operational arrangements.
• Identify architectural constraints, technical debt, risks and dependencies.
• Define coexistence and target-state messaging architectures across Microsoft 365 tenants, existing Exchange environments and retained services.
• Establish architectural principles and standards for messaging migration and modernisation.
• Design secure and resilient mail-routing architectures.
• Define accepted-domain, DNS, MX, Autodiscover and service-discovery arrangements.
• Define address-list, Global Address List and recipient-visibility strategies.
• Design calendar interoperability, free/busy and scheduling arrangements.
• Develop migration patterns for user, shared, resource and service mailboxes, distribution groups, contacts and other messaging objects.
• Establish migration sequencing covering discovery, readiness assessment, pilots, production waves, testing, cutover and post-migration support.
• Define technical entry and exit criteria for migration waves.
• Assure mail-flow continuity, including internal, external and cross-environment routing.
• Define controls for transport rules, connectors, email security and delegated access.
• Align messaging architecture with retention, compliance, eDiscovery, journalling and information-governance requirements.
• Work with security specialists to define controls using Microsoft Defender for Office 365.
• Assess dependencies involving identity synchronisation, applications, SMTP relay, collaboration services, mobile access and endpoint technologies.
• Resolve application email dependencies and define secure SMTP relay and application-to-mail integration patterns.
• Coordinate with identity, collaboration, application, network, security, EUC, service-transition and change teams.
• Review technical designs and migration approaches, providing architectural assurance.
• Support detailed migration and implementation plans while retaining ownership of the messaging architecture.
• Define rollback, recovery and contingency approaches.
• Support cutover decisions and provide technical assurance during major migration events.
• Provide guidance during early-life support and help resolve complex cross-boundary issues.
• Produce and maintain HLDs, LLDs, architecture diagrams, migration patterns, technical standards, decision records and design documentation.
• Document and communicate architectural decisions, assumptions, dependencies and risks

Skills

Exchange Online Architecture

Microsoft 365 Messaging Design

Tenant-to-Tenant Migrations

Email Security with Defender

Architecture Documentation

Tools

Microsoft 365

Exchange

Defender for Office 365

Third-Party Migration Tooling

Job description

• Own the messaging architecture and provide technical leadership across the transformation lifecycle
• Assess the current Exchange and Microsoft 365 estate, including tenants, domains, mail flow, recipients, dependencies, integrations and operational arrangements
• Identify architectural constraints, technical debt, risks and dependencies
• Define coexistence and target-state messaging architectures across Microsoft 365 tenants, existing Exchange environments and retained services
• Establish architectural principles and standards for messaging migration and modernisation
• Design secure and resilient mail-routing architectures
• Define accepted-domain, DNS, MX, Autodiscover and service-discovery arrangements
• Define address-list, Global Address List and recipient-visibility strategies
• Design calendar interoperability, free/busy and scheduling arrangements
• Develop migration patterns for user, shared, resource and service mailboxes, distribution groups, contacts and other messaging objects
• Establish migration sequencing covering discovery, readiness assessment, pilots, production waves, testing, cutover and post-migration support
• Define technical entry and exit criteria for migration waves
• Assure mail-flow continuity, including internal, external and cross-environment routing
• Define controls for transport rules, connectors, email security and delegated access
• Align messaging architecture with retention, compliance, eDiscovery, journalling and information-governance requirements
• Work with security specialists to define controls using Microsoft Defender for Office 365
• Assess dependencies involving identity synchronisation, applications, SMTP relay, collaboration services, mobile access and endpoint technologies
• Resolve application email dependencies and define secure SMTP relay and application-to-mail integration patterns
• Coordinate with identity, collaboration, application, network, security, EUC, service-transition and change teams
• Review technical designs and migration approaches, providing architectural assurance
• Support detailed migration and implementation plans while retaining ownership of the messaging architecture
• Define rollback, recovery and contingency approaches
• Support cutover decisions and provide technical assurance during major migration events
• Provide guidance during early-life support and help resolve complex cross-boundary issues
• Produce and maintain HLDs, LLDs, architecture diagrams, migration patterns, technical standards, decision records and design documentation
• Document and communicate architectural decisions, assumptions, dependencies and risks

Requirements

• Extensive architecture experience across Exchange Online, Microsoft 365 and enterprise messaging environments
• Proven experience designing hybrid and/or multi-tenant messaging architectures
• Strong experience delivering tenant-to-tenant mailbox migrations and complex coexistence arrangements
• Expert knowledge of mail routing, connectors, accepted domains, transport rules and recipient management
• Strong understanding of DNS, MX records, Autodiscover and messaging-related service discovery
• Experience designing address-list, calendar, free/busy and collaboration arrangements across multiple environments
• Proven experience defining migration strategies for user, shared, resource and service mailboxes
• Strong knowledge of email security, including Microsoft Defender for Office 365
• Good understanding of retention, eDiscovery, journalling, compliance and information-governance requirements
• Strong understanding of identity synchronisation and its relationship with messaging
• Experience designing and troubleshooting SMTP relay and application-to-email integrations
• Experience working with Microsoft and third-party messaging migration tooling
• Strong understanding of Outlook, mobile access and user experience during migration
• Experience designing migration sequencing, pilot approaches, testing, cutover and rollback strategies
• Strong architecture documentation skills, including HLDs, LLDs, diagrams, technical standards and architecture decision records
• Strong troubleshooting and analytical skills across messaging, DNS, identity, applications and client technologies
• Experience working with third-party suppliers and technical delivery partners
• Strong stakeholder-management and influencing skills
• Ability to communicate complex technical decisions clearly and practically
• Deep messaging expertise with strong architectural judgement
• Ability to assess complex existing environments, identify dependencies and design a route to the target Microsoft 365 architecture
• Ability to challenge assumptions and migration approaches that introduce unnecessary risk
• Strong communication skills when working with architects, engineers, security specialists, application teams, programme managers, suppliers and senior stakeholders

Core Competencies

Demonstrates extensive architecture experience in Exchange Online and Microsoft 365, with a strong focus on designing hybrid and multi-tenant messaging architectures. Proficient in defining migration strategies, ensuring email security, and aligning messaging architecture with compliance and governance requirements.

Highest-signal resume keywords

• Exchange Online Architecture
• Microsoft 365 Messaging Design
• Tenant-to-Tenant Mailbox Migrations
• Email Security with Microsoft Defender
• Architecture Documentation Skills

Hard Skills

• Mail Routing
• Transport Rules
• Accepted Domains
• DNS Management
• SMTP Relay
• Migration Strategies
• Calendar Interoperability
• HLDs and LLDs
• Complex Coexistence Arrangements
• Identity Synchronisation

Soft Skills

• Stakeholder Management
• Analytical Skills
• Communication Skills
• Influencing Skills
• Problem-Solving Skills

Industry Keywords

• Information Governance
• EDiscovery
• Journalling
• Compliance
• Messaging Architecture

Tools & Technologies

• Microsoft 365
• Exchange
• Microsoft Defender for Office 365
• Third-Party Migration Tooling
• Collaboration Services