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Office 365 Migration

Microsoft Exchange to Office 365 Migration

We explain how to easily carry out a Microsoft Exchange to Office 365 migration that can handle 100’s or 1,000’s or mailbox migrations to populate Office 365 simply and quickly.


With the steady advance of companies migrating data to the cloud, one of the biggest issues is that of Microsoft Exchange to Office 365 to replace the on-premise solution with a Microsoft “E” Plan and subscription based licensing.

Typically, even a small organisation may well have 250GB of data to move, larger organisations many terabytes spanning years.  The mail server contains lots of information including:

  • Email messages for both active and inactive users
  • Stubs or shortcuts
  • PSTs
  • Message journals

Relying on 3rd party products to migrate email doesn’t always go as planned.

Office 365 Migration from Exchange

The issues in Migrating to Office 365

Most Email archiving products are not very good at moving stubs or shortcuts, so users can no longer access those archived messages.

Journaling for compliance and eDiscovery will not work once you migrate.  Your existing compliance rules and internal policies or external regulations are all lost.  Workarounds do exist for some tools, but many eliminate the primary reason for migrating to Office 365.

The PST File Burden

One of the biggest headaches in migrating to Office 365 is the migration of PSTs.  Many existing PST migration methods do not validate the integrity of the messages or the existence and number and stubs.

Office 365 Migration Email Archiving Concerns

Planning to migrate from on-premise Exchange to Office 365?  Below highlight things to consider when planning to move.

  • Do I want to continue using my third-party archiving product once I migrate to Office 365?
  • How will my users be affected if I do not migrate their archived mail?
  • How will my users be affected if I delete MS Exchange stubs/shortcuts?
  • How much data do I have in my third-party archive?
  • What kind of data is it (mail, stubs, PSTs, journals)?
  • How much email do I have in the journal archive?
  • How much “dark data” do I have (archived messages from inactive users)?
  • Is the data of any value to my organisation?
  • If I have ongoing or pending litigation; can I still migrate my mail?
  • How do I manage archived email that is under legal hold?
  • Assuming I decide to migrate my archived email, should I migrate the entire archive and journal archive?
  • Will migrating my archive delay my Office 365 implementation project?

Your organisation is planning to move 1,000’s of users to Office 365 and populate this with all the users shown under your Exchange server, including staff that have left the organisation years ago?

The Exchange server is many terabytes and contains millions of messages and attachments, users emails are stubbed or shortcut links and your existing email archiving solution that was used for compliance and eDiscovery is no longer suitable.

Recent Project

We recently undertook a project with a multi-billion-pound company to migrate 5,000 users to Office 365, 40TB’s of uncompressed messages.

We achieved the following:

  • Faster direct migration of archived mail Office 365; 5+TB per server per day.
  • Highly scalable allowing for 400 simultaneous Office 365 mailbox connections per server.
  • Full Source Message ID to Exchange Message Entry ID chain of custody and reconciliation reporting.
  • Inflight MAPI property validation and source specific MAPI corruption remediation with an average of 0.001% exceptions per migrated customer.
  • Native support for Office 365 Hybrid environments and Exchange Online Archive / Personal Archive
  • Integrated Stub Management for point and click stub or shortcut discovery and rehydration.

The solution also meets SEC Rules 17a-3 and 17a-4 Guidelines, Including Ensuring WORM Compliant Storage.

  • Preserve records exclusively in a non-rewriteable, non-erasable format (i.e., WORM – Write-once, read-many);
  • Automatically verify the quality and accuracy of the storage media recording process;
  • Serialise the original and, if applicable, duplicate units of storage media, and time-date for the required period of retention the information placed on such electronic storage media;
  • Provide the capacity to readily download indexes and records preserved on the electronic storage media to any medium;
  • Audit requirements; and
  • Data encryption (in transit and on-disk).

In the past, financial services organisations had no choice but to keep their on-premises e-mail archive systems active to maintain their official books and records such as trade confirmations and email journals in WORM storage, even though they had already migrated their live email systems to the cloud.

Office 365 Migration Summary

The solution we implemented provided a fast and efficient method for migrating Email data to Microsoft Azure with the minimum of training and cost less than competing products.

If you are planning to move from on-premise Exchange to Office 365 call us on 0207 193 5760 to find out how easy it is to populate Office 365.  If you need to consolidate storage to Microsoft Azure click here.