In some environments there is a requirement for compliance or company policy to be able to retain and retrieve employee email even after the employee leaves a company.
In traditional on premise Exchange scenarios, backup software maybe used where let’s say if the email needed to be retrieved 8 months ago and you only keep email retained for 30 days, you might need to go back to tape and retrieve it.
Microsoft does not keep backups of your data so it’s important before migrating to Office 365 to have an idea of its limitations and how you will get around them. The solution might be to develop new policies and procedures or to acquire new software that can go into Office 365 and backup mailboxes. It might even be to remote copy mailboxes or convert to PST files to keep on premise and on hand.
There are a few things to need to take stock of
1) How are you currently keeping deleted items or deleted users emails?
2) How far back are you going?
3) Do I need to incorporate some mix of on premise and Office 365 functionality
4) Make sure you share this information and document everything
First in the on-premise world your default mailbox size is typically 2 GB and in Office 365 you don’t really have to think about this anymore since every user of Enterprise plans are given 50 GB. On top of this if your users incorporate archives, the archives give users unlimited space. So essentially if managed properly, Office 365 gives your users 50 GB to unlimited space right now.
Great, What about accessing users deleted items, When a user deletes an email in Office 365, it is automatically recoverable for up to 15 days, and that setting can be changed in the compliance center for up to 30 days.
What about anything beyond that?
If you want to keep emails available for ever, you can place a users mailbox on litigation hold. Now there is some argument on space available for litigation hold. Microsoft’s documentation says 30 days per mailbox, but I’ve also heard there is no limit. I am trying to track down the correct answer.
To search for messages in users mailbox that are in litigation hold you can use the Compliance search in the Office 365 compliance center.
There are backup software out there such as commvault to offer Office 365 backups.
With proper strategy and knowledge, email retention should not be a barrier to moving to Office 365.