Microsoft keeps the Microsoft 365 service running, but the data in it is the customer's responsibility. Built-in recycle bins and retention settings are designed for short-term recovery and compliance, and they do not give you an independent copy that survives a deleted account, a mistaken bulk change, a compromised administrator or a lapsed subscription. A Synology NAS can provide that copy. Using Synology's Active Backup for Microsoft 365 package on a supported model, the NAS connects to your tenant and regularly downloads mailboxes, OneDrive files, SharePoint sites and Teams data to storage you own, with version history and the ability to restore individual items. For an SME already buying a NAS, it adds Microsoft 365 protection without a per-user backup subscription.
Why does Microsoft 365 need its own backup?
| Situation | What Microsoft 365 gives you by default |
|---|---|
| A user deletes an email | Recoverable for a limited period, 14 days by default and extendable to 30 |
| A file is deleted from OneDrive or SharePoint | Held in recycle bins for up to 93 days in total |
| A staff member leaves and the licence is removed | Mailbox and OneDrive are removed after a grace period unless action is taken |
| Ransomware encrypts synced files | Version history may help, within its limits |
| An administrator account is compromised | The attacker can change retention and purge data |
| You need a file as it was a year ago | Not available unless retention policies were set up in advance |
The periods shown are Microsoft's documented defaults at the time of writing and depend on your plan and settings; check your own tenant. Microsoft also sells its own backup service for Microsoft 365 as a paid add-on, which is another route to consider. The underlying reasoning is set out in why Microsoft 365 is not your complete backup strategy.
Source: Microsoft 365 service documentation on deleted item retention and recycle bins. Compiled 12 Nov 2026.
What can a Synology NAS back up from Microsoft 365?
| Service | Covered |
|---|---|
| Exchange Online | Mail, attachments, contacts, calendars; shared and archive mailboxes where supported |
| OneDrive for Business | Files and folders, with versions |
| SharePoint Online | Site document libraries and lists |
| Microsoft Teams | Team files and channel content, within what Microsoft's interfaces expose |
Coverage of individual item types, particularly in Teams, changes as Microsoft and Synology update their software. Confirm the current list in Synology's documentation against what you need to keep.
Source: Synology Active Backup for Microsoft 365 documentation. Compiled 12 Nov 2026.
How does it work?
- Install the package on a supported NAS and sign in with a Microsoft 365 administrator account to authorise access to the tenant.
- Choose what to protect. All users, or selected accounts, sites and teams. New users can be added automatically.
- Set the schedule and retention. Continuous or scheduled backup, and how long versions are kept.
- The NAS downloads the data over your internet connection. The first run is the long one; later runs fetch changes.
- Restore through a portal. Administrators, and users if you allow it, can search for and restore single emails, files or whole accounts, or export them.
How much storage is needed?
CALC. Twenty-five users averaging a 10GB mailbox and 30GB in OneDrive: 25 x (10 + 30) = 1,000GB. Add 200GB of SharePoint: 1,200GB. Allow half as much again for versions and growth: 1,200 x 1.5 = 1,800GB, about 1.8TB. Synology's software stores identical content once, which usually reduces the real figure, but plan on the higher number. Your tenant's admin centre shows actual usage per user and site; use those figures in place of these averages.
The first backup also depends on your internet line. Downloading 1,200GB over a 500 Mbps connection at about 62 MB/s takes 1,200,000 / 62 = 19,355 seconds, roughly 5.4 hours in theory. In practice Microsoft limits how fast data can be pulled, so allow days for the first full run.
What does it need?
- A supported NAS model. The package runs on selected models, generally Plus series and above. Check the compatibility list.
- Capacity as sized above, on redundant drives.
- A reliable internet connection for the NAS.
- A Microsoft 365 administrator to grant and maintain access.
Microsoft protects the service. You protect the data. A copy on storage you own is the difference between asking for your data and having it.
What should you plan before switching it on?
- The NAS becomes a store of all company email and files. Secure it accordingly: strong administrator accounts with two-factor sign-in, no direct internet exposure, encryption where appropriate.
- Who may restore what. Self-service restore is convenient; decide whether users should see only their own data.
- Retention versus privacy. Keeping everything forever conflicts with the Personal Data Protection Act's requirement not to retain personal data longer than needed. Set a retention period that matches your business and legal needs.
- Leavers. Decide how long a departed employee's backed-up mailbox is kept.
- The backup needs a backup. Replicate the NAS to a second device or cloud target. See the 3-2-1 backup rule.
- Monitoring. Authorisation tokens expire and jobs fail. Someone should receive the alerts.
- A restore test. Recover a mailbox item and a SharePoint file before you need to.
How does it compare with a cloud backup service for Microsoft 365?
| Synology NAS | Third-party cloud backup service | |
|---|---|---|
| Cost model | Hardware once; no per-user licence on supported models | Per user, per month |
| Where data is held | Your premises | Provider's data centres |
| Upkeep | Yours: hardware, updates, monitoring | Provider's |
| Off-site by default | No; add replication | Yes |
| Also backs up PCs and servers | Yes, with Active Backup for Business | Depends on the service |
For a business with no IT upkeep capacity at all, a managed cloud service may be the better fit. For one that already runs a NAS, adding Microsoft 365 backup to it is economical. For how a NAS compares with Microsoft 365 as a place to work, not just a backup target, see NAS vs cloud storage.
Buying in Singapore
Plus-series NAS: the Synology DS425+ (S$853.20), DS925+ (S$1,260) or DS1525+ (S$1,800), with Seagate IronWolf Pro drives from S$390. Second copy: the Synology ActiveProtect DP320 (S$2,611.20) (listed 12 Nov 2026; prices change; ask for a current quotation). Tell us your user count and tenant storage and we will confirm package support for the model before quoting. To start, use Request for Quotation on the product page, call (65) 6978 3502, email Sales@sourceit.com.sg or use our contact page.
Frequently asked questions
Can a Synology NAS back up Microsoft 365? Yes. On supported models, Synology's Active Backup for Microsoft 365 package backs up Exchange Online mailboxes, OneDrive for Business, SharePoint Online and Teams data to the NAS.
Does Microsoft back up Microsoft 365 data for you? Microsoft keeps the service available and offers recycle bins and retention features, but protecting the data against deletion, compromise and long-term loss is the customer's responsibility.
Is there a per-user licence for backing up Microsoft 365 to a Synology NAS? Synology provides the package without per-user licence fees on compatible models. Confirm current terms and model support with Synology.
How much NAS storage does Microsoft 365 backup need? Add up mailbox, OneDrive and SharePoint usage from your admin centre and allow about half as much again for versions and growth.
SourceIT Approved
Researched and verified by the SourceIT team for Singapore buyers.
