Mailbox-level backups in Office 365

Executive summary: there aren’t any, so plan accordingly.

Recently I was working with a customer (let’s call him Joe, as in “Joe Customer”) who was considering moving to Office 365. They went to our executive briefing center in Austin, where some Dell sales hotshots met and briefed them, then I joined in via Lync (with video!) for a demo. The demo went really well, and I was feeling good about our odds of winning the deal… until the Q&A period.

“How does Office 365 provide mailbox-level backups?” Joe asked.

“Well, it doesn’t,” I said. “Microsoft doesn’t give you direct access to the mailbox databases. Instead, they give you deleted item retention, plus you can use single-item retention and various types of holds.” Then I sent him this link.

“Let me tell you why I’m asking,” Joe retorted after skimming the link. “A couple of times we’ve lost our CIO’s calendar. He uses an Outlook add-in that prints out his calendar every day, and sometimes it corrupts calendar items. We need to be able to do mailbox-level backups so that we can restore any damaged items.”

At that point I had to admit to being stumped. Sure enough, there is no Office 365 feature or capability that protects against this kind of logical corruption. You can’t use New-MailboxExportRequest or the EAC to export the contents of Office 365 mailboxes to PST files. You obviously can’t run backup tools that run on the Exchange server against your Office 365 mailbox databases; there may exist tools that use EWS to directly access a mailbox and make a backup copy, but I don’t know of any that are built for that purpose.

I ran Joe’s query past a few folks I know on the 365 team. Apart from the (partially helpful) suggestion not to run Outlook add-ins that are known to corrupt data, none of them had good answers either.

While it’s tempting to view the inability to do mailbox-level backups as a limitation, it’s perfectly understandable. Microsoft spent years trying to get people not to run brick-level backups using MAPI. The number of use cases for this feature is getting smaller each year as both the data-integrity and retention features of Exchange get better. In fact, one of the major reasons that we now have single-item recovery in its current form is because customers kept asking for expanded tools to recover deleted items, either after an accidental deletion or a purge. Exchange also incorporates all sorts of infrastructure to protect against data loss, both for stored data and data in transit, but nothing really helps in this case: the corrupt data comes from the client, and Exchange is faithfully storing and replicating what it gets from the client. In fairness, we have seen business logic added to Exchange in the past to protect against problems caused by malformed calendar entries created by old versions of Outlook, but clearly Microsoft can’t do that for every random add-in that might stomp on a user’s calendar.

A few days after the original presentation, I sent Joe an email summarizing what I’d found out and telling him that, if mailbox-level backup was an absolute requirement, he probably shouldn’t move those mailboxes to Office 365.

The moral of this story, to an extent that there is one, is that Microsoft is engineering Office 365 for the majority of their users and their needs. Just as Word (for instance) is supplemented by specialized plugins for reference and footnote tracking, mathematical typesetting, and chemistry diagrams, Exchange has a whole ecosystem of products that connect to it in various ways, and Office 365 doesn’t support every single one of those. The breadth and diversity of the Exchange ecosystem is one of the major reasons that I expect on-premises Exchange to be with us for years to come. Until it finally disappears, don’t forget to do some kind of backups.


Filed under Office 365, UC&C

8 responses to “Mailbox-level backups in Office 365

  1. Peter Bowley

    I’ve used the message ops migrator for this very task in the past;

    Although many a person is mortified on the creation of psts it’s been the best option I could find.


  2. I’ve got a few awful calendar editing apps to deal with, but almost all of the restores are due to a user deleting a folder tree. Without the ability to restore the folder structure (with items in the right folders), single-item recovery is kind of a giant mess. You’d think with the lagged copies that exist out there, it should be technologically feasible to create a temp “snapshot” of the mailbox from a point in time.

  3. Office 365 activate daily backups for all selected users.Office 365 backup of your Email, Calendar, Contacts.

    CloudAlly provides unlimited archives retention and unlimited archive storage. At any time you can downland a snapshot of your data from any data in the past or restore it directly to your office 365 account.
    For more help check this:

  4. Austin McCollum

    For this particular person, there’s a feature enabled, “Calendar Version Store” that already protects against calendar corruption. CVS keeps each version of every calendar item in a special place in the dumpster of a mailbox for up to 120 days. For other types of mailbox corruption, “In place hold” actually achieves this because of the copy on write feature saves each version of an item in the versions folder of the dumpster. Instead of trying to do mailbox level backups, enable VIPs with in place hold!

  5. Dylan

    Great post Paul. Stumbled across it while researching this exact issue – just had a user (VIP of course) accidentally delete a large number of subfolders in their Office365 mailbox from their iPhone. While the items are of course retained, the folder structure isn’t, so it’s a mammoth job to try and get these back. Pretty rare and specific circumstances, but when they occur it seems there’s nothing that can be done.

    • robichaux

      Since I wrote this post, several products have emerged to solve this problem… but only if you install and use them BEFORE someone deletes something important. We need an Office 365 time machine.

  6. The article deals with the discussion about measures to perform Office 365 Backup. It involves backing up of mailboxes of Office 365 user account and archiving them into a particular file formats for local storage.

  7. D.McBride

    My boss told me to look at a few Office 365 mailbox backup solutions, mainly CodeTwo (, Cloudally (, CloudBacko (, Spanning ( etc. They all seem okay, except their prices vary a lot. Anyone can share your experience in any of them? Appreciated 😀

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