United Kingdom | What should the target be Mailbox or Online Archive - Part 1?

Nick Middleton - 15.01.202020200115

What should the target be Mailbox or Online Archive – Part 1?

United Kingdom | What should the target be Mailbox or Online Archive - Part 1?

As part of a legacy email archive migration to Office365 we get asked what’s the difference between migrating the archive data to Primary Mailbox vs Online Archive Mailbox. Both options have positives and negatives and its important to understand them so you can reach the best route for the end user.

Primary Mailbox

Positives

  • The users legacy data is merged back into their mailbox giving them a single point of view on all their data. Depending on how the legacy archiving platform is deployed this might be a change in behaviour i.e. if users access the archived content via a web page then they won’t be used to this experience.
  • All the user’s data can be cached to their Outlook client, meaning that if they are offline they can still access it.
  • Going to mailbox represents the least change to the user behaviour (assuming you have shortcuts)

Negatives

  • Legacy archive data must be populated either back into the on-premises Exchange before the mailbox migration (which can cause disk space issues on Exchange) or after into Office365. If you migrate the data after the mailbox migration the user could be without access to the legacy archived data for a period of time and this is dependent on how long it takes to migrate. Remember the primary goal of archiving was and is to keep the mailbox sizes small this means undoubtably there is more data in the user’s legacy archive then in their mailbox.
  • Depending on how aggressive your archiving policy is you may have a lot of data to go back into the mailbox, this then must be cached back to Outlook. Even for 100 users this could be terabytes of data either coming from your Exchange servers or coming down the pipe for Office365. You can of course mitigate this by changing the amount of data Outlook caches, but this can still be an issue.
  • As mentioned above with the caching this can impact the users experience as users Outlook will be caching (possibly for several hours) this will cause latency for the user when they are working within Outlook.
  • Shortcuts to your legacy archive data can also cause some pain if you go to mailbox, as they are not supported by Microsoft in Office365. So, this means you should delete them before you move the mailbox. This in turn (if this is the primary way your users access the data) extends the period the users will be without their legacy data as you have to delete shortcuts, migrate mailbox and then migrate the legacy archive data.
  • Once the mailbox is in Office365 the maximum size it can be is 100GB if you have E5 licensing (Link). If you have data retention / legal hold in place for say 7 years, 100 GB is not a lot and you may find you end up having to enable Online Archives in the future anyway.

Online Archive Mailbox

Positives

  • Legacy archive data can be migrated before the mailbox is moved, assuming you have the hybrid Exchange environment setup, as you can provision the Online Archive Mailbox remotely i.e. the mailbox is on-premises and the Online Archive is in Office365. This then allows the users to have uninterrupted access to the legacy data by communicating to them that they will see the Online Archive appear in their Outlook and data being populated into it. They will then see their shortcuts disappear (assuming you have them) and from that point they can go to the Online Archiving for the legacy data.
  • No long resyncs for Outlook as the Online Archive does not get cached hence Outlook does not need to pull all that data down.
  • There should be no impact on your On-Premises Exchange’s capacity.
  • Online Archives can auto-expand (if you have E3 or E5 licensing and it is set in your environment) this means you don’t have to worry about the user running out of space.

Negatives

  • You cannot cache the Online Archive in Outlook; this means when the user is offline, they cannot access the data in it.
  • The user has a change in behaviour when using an Online Archive, in most cases they would have been used to a single point of view on their data i.e. in their mailbox, but now they have two places to view data. First in the mailbox and the second in the Online Archive.

As you can see it is not a simple decision to make as neither option is without its down sides. In part 2 I will be exploring the various approaches you can use to mitigate some of the cons but I hope this has give you a few things to think about while making, what is, a critical call in the life of a migration project.

United Kingdom | What should the target be Mailbox or Online Archive - Part 1?

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United Kingdom | What should the target be Mailbox or Online Archive - Part 1?

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