Office 365 Migration


Lexicast, a leading accounting firm in the Milton Keys, had the goal of transitioning their email from an On-Premise Exchange Server to Office 365 Hosted Exchange.

The Challenge:

Lexicast wished to refresh its technology infrastructure significantly to accommodate office 2010 users. As the users had 2010 versions of Office installed, and in order to migrate away from their existing 2010 Microsoft Exchange Server and move all their email services, mailboxes, calendars, contacts, and tasks to Microsoft’s Office 365 Hosted Exchange platform. During this time even simple tasks became time-consuming and complicated. They knew that their environment had to be stabilized, and centralised. They did not want to burden their internal workers with finding ways to combine different platforms, so they contacted LEO24 for suggestions. Cedex sought to implement a scalable environment that was secure, reliable, and cost-effective. In addition, they need to maintain its internal Active Directory infrastructure. As a hybrid Cloud/On-Premises Microsoft solution, the following issues arose.

  • Moving all 50+ users’ Mailboxes, Emails, Folders, Contacts, Calendars, Tasks, and emails into the cloud so that they would be properly preserved and accessible in the future
  • Users should be able to make the switch with minimal assistance and minimal downtime by having the cutover occur on the weekend so that they may enter Monday ready to use the new system.
  • Keep the current active directory servers running within their organisation and work with the cloud system
  • Make sure the on-premises Active Directory domain is compatible with the new cloud email system.
  • Lexicast should be able to de-commission the exchange server without losing any data, admin functions or network functionality


LEO24 collaborated with the Lexicast staff to create a schedule and migration calendar, after completing the proof of concept with the O365 contract. A two-week preparation preceded a weekend migration, as follows:

  • Before setting up all the Office 365 email services, LEO24 purchased and set up all the necessary licences and services, verified by the Cedex domain, created all the users/groups/public folders in the cloud, and performed a “pre-migration” move of the bulk of the “Cedex” emails, contacts, calendars, etc..
  • Upon confirmation that on-premises exchange server data had successfully been moved to O365, we created documentation to notify users what was happening, how to add their new email account to their devices, how to contact us in the event of problems.
  • We did the cutover on a weekend and adjusted MX records, hosted DNS records, and rerouted Lexicast email to new cloud systems
  • We ran a final migration after verifying that the email was properly routing and moved all the remaining email data from the on-prem Exchange server to O365.
  • We were able to determine that all of our email, contact, calendar, and other data had been mirrored to the cloud and worked on-site the following Monday morning to ensure that users were connected to the new system and that all their data was available.
  • We made sure that Lexicast employees had all their data transferred to O365 Hosted Exchange and that no problems had arisen before the 1-week included support period was over.
  • We confirmed that the cloud email and all on-prem data and domain servers still functioned after monitor 4 weeks de-commissioned their Exchange server on-premises.


With the assistance of LEO24, Lexicast migrated all of their email data and services from their on-premise Exchange server to Office 365’s Hosted Exchange platform while maintaining internal Active Directory domain functionality with no lost data and zero downtime.

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