Restow vs MailStore Server
MailStore Server, owned by OpenText, is a self-hosted email archive for Windows. It is licensed per user with a perpetual right of use and a separate Update & Support subscription, and it holds an IDW PS 880 certification in Germany, Austria and Switzerland.
The short answer
MailStore fits companies that need a certified email archive on Windows today, with a perpetual license and a large installed base in German-speaking countries.
Restow fits if you want backup, restore and an archive in one Linux installation, with a weekly restore test. Its archive has a hash chain and search in every edition, plus journaling, retention and legal hold from Business, but no third-party certification; MailStore has the longer track record.
At a glance
| Aspect | Restow | MailStore |
|---|---|---|
| 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. | Per user, perpetual right of use, plus Update & Support for 1 to 3 years. Reactivating lapsed support costs 70 % of the current list price. |
| Where it runs | Self-hosted: one Docker Compose stack on a Linux server or VM you control. | Self-hosted on Windows; Windows Server above 25 users. |
| Where backups are stored | Your choice: local disk, S3-compatible object storage, NFS or SMB, in the region you pick. | File system or NAS. No S3, Object Lock or WORM documented. |
| 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. | Email archiving for Microsoft 365, Exchange, Google and IMAP. |
| Restore testing | Weekly sampled restore: data is read back through the restore path and compared byte for byte. | A schedulable integrity check (VerifyStore); no automated test-restore documented. |
| 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 openly specified. Exports as EML, MSG or PST. |
Where MailStore is strong
- IDW PS 880 certification for Germany, Austria and Switzerland.
- A perpetual license: the software keeps running after support lapses.
- Mature, widely used archive with many export paths.
- Signed exports can be verified with OpenSSL.
Where Restow is different
- Linux and Docker instead of Windows Server.
- S3-compatible object storage as well as local disk, NFS or SMB.
- Backup and non-destructive restore of whole mailboxes and OneDrive, with a weekly restore test.
- All updates included for as long as Restow is actively developed; no separate update subscription.
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.
MailStore: the facts, with sources
Each line is taken from MailStore'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 |
|---|---|---|
| Self-hosted, Windows only. Once an installation passes 25 users, a full Windows Server edition is required. | System Requirements | Official source |
| Licensed per user with a perpetual right of use. A separate, time-limited Update & Support subscription (1, 2 or 3 years, Standard or Premium) is sold alongside it; the software keeps running after that subscription lapses. | Ordering and Licensing FAQ | Official source |
| Reactivating a lapsed Update & Support subscription is not a normal renewal: the vendor's own published terms price it as an "upgrade" at 70% of the current list price of the existing licenses. | Ordering and Licensing FAQ | Official source |
| A starter package covers 5 users. | Ordering and Licensing FAQ | Official source |
| An IDW PS 880 software certification exists for Germany, Austria and Switzerland: a real, named German auditing-standard certificate, not a self-declared claim. Publicly downloadable certificate PDFs go up to version 23.4; the current certificate is available on request. | Rechtssicherheit (legal certainty) | Official source |
| Storage is file system or NAS. SQL/PostgreSQL-backed stores have taken no new installations since version 26.1 and are being phased out entirely by the end of 2026. No S3, Object Lock or WORM storage support is documented. | Storage Locations | Official source |
| Export formats: EML/MSG, PST, or direct export into an M365/Exchange/Google/IMAP mailbox with folder structure preserved; signed exports can be verified with OpenSSL. The internal storage format itself is not openly specified. | Exporting Email | Official source |
| A schedulable integrity check ("VerifyStore") exists; an automated end-to-end test-restore comparable to reading data back and diffing it is not documented. | Maintenance and Repair | Official source |
| Not open source: proprietary commercial software owned by OpenText. | Absence checked across the pages above | Checked: not found |
Frequently asked
Does Restow also archive email, like MailStore?
Yes, since 0.1.0: every edition archives Microsoft 365 and IMAP mail with a SHA-256 hash chain and full-text search; Business and Service Provider add Exchange Online journaling, enforced retention and legal hold. MailStore holds an IDW PS 880 certificate; Restow has none, and is younger.
What happens when MailStore Update & Support lapses?
The software keeps running. Reactivating support later is priced as an upgrade at 70 % of the current list price of your licenses, according to MailStore's published terms.
Can I move from MailStore to Restow?
Partly. Restow imports a MailStore export as EML or MSG files (a folder tree, or a ZIP of it) into a legacy mailbox that you can browse, restore into Microsoft 365 or IMAP, download and optionally archive. MailStore's internal archive format cannot be read, so export from MailStore first. Restow exports mail as EML in a ZIP or as MBOX, with checksums; PST export is planned.