Case Study
Financial Services

O365 Migration

December 31, 2020

Delivering a successful migration of 35,000 user mailboxes to O365

Our client is among the largest institutions in the financial, utility, and telecommunication sectors in Australia servicing customers across Australia, New Zealand and Asia. Due to Microsoft 2010 nearing end of life, our client wanted to migrate all of their employees toO365 to leverage new collaborative tools, security features and functionality while reducing maintenance cost by moving all mailboxes to Exchange Online.

Operating a large environment of 55,000people, they were struggling with formulating a cohesive and phased migration plan. Operating such a complex application profile posed a serious obstacle to implementing change across the entire organisation.

The main challenges faced by our client were:

  • They operated a complex con-premise exchange environment.
  • The Microsoft environment integrated with more than ~4,000 applications.
  • They lacked a deployment strategy for upgrading around ~50,000 machines to O365.
  • They operated a diversified user base of more than 35,000 employees spread across the world.

The Opportunity

The O365 migration had to be completed within2 years as the client was already paying Microsoft for an O365 subscription for 40,000 licenses as per agreement. This, coupled with existing infrastructure and support costs for the ‘On-premise’ environment and the Office 2010currency expiry in FY2020, posed serious risks to business operations.

Seisma was engaged to develop and implement a project plan for O365 migration covering testing and remediation of all applications, upgrading all machines to O365 and migrating users’ mailboxes to EXO. The success of O365project was dependent on Seisma’s ability to create an exhaustive roll-out plan based on expected timelines and staggering it to meet every stakeholders’ needs.

Our solution

Our team was able to leverage our O365 migration methodology to develop a tailored migration approach to assess the complex current exchange landscape and recommend solutions.

The migration strategy was implemented in three phases:

  1. Assessment and feasibility: Understanding the Exchange landscape through workshops and deep-dive sessions with technical architects and SMEs. We developed an assessment tool that provided predictability and consistency in assessing each business unit and categorising them into buckets. This enabled us to plan upgrade and migration timelines while concurrently performing testing and remediation for business units integrating with MS Office products.
  2. Planning and decision making: Enrolling key stakeholders to agree on migration options was key. Our consultants conducted sessions with stakeholders to socialise the software upgrade and migration strategy and agree on recommendations foreach business unit.
  3. Execution and governance: By developing an upgrade and migration roadmap, we developed separate ‘software upgrade’ and ‘mailbox migration’ roadmaps based on findings during the assessment and feasibility phase. A business case with end-to end program costings and timelines was developed and presented to the investment committee for endorsement. A tightly controlled governance framework was proposed to ensure minimum deviation from goals and no cost wastages from scope creep.

Results and benefits

Seisma delivered to our client a successful migration of all 35,000 user mailboxes to O365.

  • The roadmap, migration strategy and business case with a concise, predictable and clear direction to deliver the successful migration of more than 35,000 mailboxes.
  • Yearly cost savings of more than AUD$2million in infrastructure and support costs.
  • Delivery of a collaborative anytime, anywhere platform accessible from allocations, on any device helped in creating substantial performance improvements for client teams.
  • Delivered an ‘evergreen’ model enabled client to easily push out future Office updates as part of BAU process, thus delivering greater ability to manage and deliver change.


O365 migrations pose a big challenge for large organisations due to the large number of legacy platforms, applications and operating systems in place. It is necessary to cover all aspects and every business unit since there are significant gaps in working practices, customisations, and controls.

A strong migration strategy goes a long way in ensuring the organisations preparedness in meeting future challenges posed by ever changing technological advancements.

Such an initiative requires building a strong platform by incorporating best practices vital for implementing a complex project like O365 migration and this can generally take between 12-18 months.

*This case study is sourced from acquired company coIB's archives. Exact publish date not known.


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