M365 Architect - Exchange/Messaging

Role summary

M365 Architect - Exchange/Messaging is a full-time role at Methods Business and Digital Technology in London, England, United Kingdom (remote). Posted 2026-09-02. Experience level: 10+.

Job title

M365 Architect - Exchange/Messaging

Company

Methods Business and Digital Technology

Location

London, England, United Kingdom

Work arrangement

remote

Employment type

full-time

Category

Logistics & Warehousing

Experience level

10+

Date posted

2026-09-02

Job description

Methods Business and Digital Technology Limited

Methods is a £100M+ IT Services Consultancy who has partnered with a range of central government departments and agencies to transform the way the public sector operates in the UK. Established over 30 years ago and UK-based, we apply our skills in transformation, delivery, and collaboration from across the Methods Group, to create end-to-end business and technical solutions that are people-centred, safe, and designed for the future.

Our human touch sets us apart from other consultancies, system integrators and software houses - with people, technology, and data at the heart of who we are, we believe in creating value and sustainability through everything we do for our clients, staff, communities, and the planet.

We support our clients in the success of their projects while working collaboratively to share skill sets and solve problems. At Methods we have fun while working hard; we are not afraid of making mistakes and learning from them.

Predominantly focused on the public-sector, Methods is now building a significant private sector client portfolio.

Methods was acquired by the Alten Group in early 2022.

About the role

We are looking for an experienced Exchange / Microsoft 365 / Messaging Architect to join a major technology transformation programme and take ownership of the messaging architecture and migration strategy.

This is a key architecture role responsible for designing a secure, resilient and supportable messaging environment while enabling users and services to transition from existing platforms and configurations into the target Microsoft 365 environment.

You will assess the existing Exchange and Microsoft 365 estate, understand the complexities of domains, mail flow, recipients, security controls and application integrations, and develop a practical architecture that supports both coexistence and eventual transition to the target state.

A significant part of the role will involve designing how messaging services operate during the transition period. This will include mail routing, accepted domains, DNS, Autodiscover, recipient management, calendars, free/busy, shared and resource mailboxes and application-relay dependencies.

You will also define the migration patterns and sequencing required to move users and messaging objects safely, ensuring that mail flow, data integrity, security, compliance and the end-user experience are protected throughout the programme.

The successful candidate will combine deep technical expertise in Exchange Online and Microsoft 365 with strong enterprise architecture, migration and stakeholder-management skills.

What you will do

As the Exchange / Microsoft 365 / Messaging Architect, you will own the messaging architecture and provide technical leadership across the transformation lifecycle.

You will:

Assess the current Exchange and Microsoft 365 estate, including configuration, tenants, domains, mail flow, recipients, dependencies, integrations and existing operational arrangements.

Identify architectural constraints, technical debt, risks and dependencies that could affect the transformation.

Define coexistence and target-state messaging architectures across relevant 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 across existing and target environments.

Define accepted-domain strategies and address dependencies associated with domain ownership, DNS and mail routing.

Design DNS, MX, Autodiscover and service-discovery arrangements required to support coexistence and migration.

Define address-list, Global Address List and recipient-visibility strategies appropriate to the target environment.

Design calendar interoperability, free/busy and scheduling arrangements during the transition.

Develop migration patterns for user, shared, resource and service mailboxes, as well as distribution groups, contacts and other messaging objects.

Define appropriate approaches for different mailbox and messaging-object types, recognising that not all services will have the same migration requirements.

Establish migration sequencing, including discovery, readiness assessment, pilots, production waves, testing, cutover and post-migration support.

Define technical entry and exit criteria for messaging migration waves.

Design and assure mail-flow continuity throughout migration, including internal, external and cross-environment routing.

Define controls for transport rules, connectors, email security and delegated access.

Ensure messaging architecture aligns with organisational requirements for retention, compliance, eDiscovery, journalling and information governance.

Work with security specialists to define appropriate controls using capabilities such as Microsoft Defender for Office 365.

Assess dependencies between messaging and identity synchronisation, applications, SMTP relay, collaboration services, mobile access and endpoint technologies.

Work with application teams to understand and resolve dependencies where applications send or receive email.

Define patterns for SMTP relay and application-to-mail integrations, ensuring they are secure, supportable and aligned with the target architecture.

Coordinate with identity, collaboration, application, network, security, EUC, service-transition and change teams to ensure messaging dependencies are properly managed.

Review technical designs and migration approaches produced by engineering and delivery teams, providing architectural assurance.

Support the development of detailed migration and implementation plans while retaining ownership of the overall messaging architecture.

Define rollback and recovery approaches for messaging migrations and ensure appropriate contingency arrangements are considered.

Support cutover decision-making and provide technica