Restow vs Synology Active Backup for Microsoft 365
Active Backup for Microsoft 365 is a free add-on for Synology NAS devices. There is no license and no account limit; you need a Synology NAS with enough storage. It is the most common self-hosted Microsoft 365 backup in small businesses and homelabs.
The short answer
Synology fits if you already own a Synology NAS: Microsoft 365 backup costs nothing extra, covers SharePoint and Teams, and exports to PST, ICS and CSV.
Restow fits if you want the same self-hosted idea without being tied to one hardware brand, plus a weekly restore test, IMAP mailboxes and, for MSPs, many tenants in one installation. Restow Community is free as well.
At a glance
| Aspect | Restow | Synology |
|---|---|---|
| Price model | Community free. Business €595, Service Provider €1,950, one-time, net (pre-sale until release: €476 and €1,560). No per-user fee. | Free add-on, no license, unlimited accounts. Requires a Synology NAS. |
| Where it runs | Self-hosted: one Docker Compose stack on a Linux server or VM you control. | On a Synology NAS with DSM. |
| Where backups are stored | Your choice: local disk, S3-compatible object storage, NFS or SMB, in the region you pick. | The NAS itself. |
| Microsoft 365 coverage | Exchange Online mail, calendar, contacts; OneDrive; IMAP mailboxes; Linux and macOS servers and clients (file-level agent); imported mail files. No SharePoint or Teams in version 1. | Exchange mail, contacts, calendars; OneDrive; SharePoint libraries and lists; Teams posts. |
| Restore testing | Weekly sampled restore: data is read back through the restore path and compared byte for byte. | Not described on the pages checked. |
| Source code and exit | AGPL-3.0 core, source-available Business and Service Provider modules, open documented storage format with a standalone restore tool. | Proprietary, internal format not open. Exports to EML, PST, CSV, ICS and HTML. |
Where Synology is strong
- No license cost at all on existing Synology hardware.
- Covers SharePoint and Teams.
- Continuous, scheduled or manual backup, unlimited recovery points.
- Exports mail to PST and EML.
Where Restow is different
- Runs on any Linux server or VM, not only on one vendor's NAS.
- Writes to local disk, S3-compatible object storage, NFS or SMB, so an off-site copy is easy.
- A weekly restore test per mailbox that reads data back and compares it.
- IMAP mailboxes too, and multiple tenants for service providers (Service Provider edition).
- Open source core and an open storage format with a standalone restore tool.
What Restow does not do (yet)
- Restow does not back up SharePoint or Teams in version 1.
- The audit log, SSO and roles are in development for Business.
- Licenses include no support; setup is available on quote.
- The server and endpoint agent runs on Linux and macOS, file-level; Windows is planned.
- Restow 0.1.0 is a beta: do not use it as your only backup.
Synology: the facts, with sources
Each line is taken from Synology's own documentation unless the rating says otherwise. "Checked: not found" means we looked in the named sources and did not find it, which is not proof that it does not exist.
| Fact | Source | How solid |
|---|---|---|
| Active Backup for Microsoft 365 is a free add-on for Synology NAS servers; no licenses are required and the number of accounts is unlimited, as far as storage allows. | Synology: Active Backup for Microsoft 365 | Official source |
| Runs only on a Synology NAS with DSM; deduplication needs an x64 model with the Btrfs file system. | Synology: Active Backup for Microsoft 365 | Official source |
| Backs up Exchange Online (mail, contacts, calendars), OneDrive for Business, SharePoint Online document libraries and lists, and Teams posts and settings. | Synology: technical specifications (DSM 7.3) | Official source |
| Scheduled, manual and continuous backup modes; retention either for a set period or all versions, with unlimited recovery points. | Synology: technical specifications (DSM 7.3) | Official source |
| Exports mail to EML or PST, contacts to CSV, calendars to ICS and Teams posts to HTML. | Synology: technical specifications (DSM 7.3) | Official source |
| No automated restore verification was described on the pages checked, and no IMAP backup. | Synology: technical specifications (DSM 7.3) | Checked: not found |
Frequently asked
Is Synology Active Backup for Microsoft 365 really free?
Yes. Synology calls it a free add-on for Synology NAS servers and states that no licenses are required. The cost is the NAS and its disks.
Is Restow free too?
Restow Community is free for one organization, with no mailbox limit. Business and Service Provider are one-time purchases for features such as the audit log, SSO and multiple tenants.
Does Restow back up SharePoint and Teams like Synology?
No, not in version 1. Synology covers them and Restow does not.