Align mailboxes between Microsoft 365 and IMAP systems – including discovery, mapping and repeatable delta runs.
Move email, calendars and files between stacks.
StackShift migrates and synchronizes email, calendars, contacts and files between Microsoft 365 and self-hosted systems, as well as between tenants and like-for-like platforms.
Access and billing via my.onesystems.ch. The portal at app.stackshift.ch requires an existing account.
One platform for controlled migrations
StackShift replaces ad-hoc scripts with auditable sync plans: connect source and target, map users, validate, then synchronize.
Calendars
Move events via Microsoft Graph or CalDAV. Pair calendars deliberately instead of copying everything blindly.
Contacts
Synchronize address books via Graph or CardDAV – including Mailcow/SOGo and other DAV stacks.
Files
Mirror OneDrive and Nextcloud/WebDAV bidirectionally. Folder structure is preserved, with optional WebDAV subfolders.
Which systems does StackShift speak?
The production-approved connectors – plus Google Workspace in beta, not generally released.
Microsoft 365
Source and target via Microsoft Graph – including tenant to tenant: email, calendars, contacts and OneDrive using the app credentials from the connection profile.
IMAP & Mailcow
Classic mailboxes, Mailcow, Stalwart and comparable IMAP servers – including an optional DAV login for SOGo.
CalDAV / CardDAV
Run calendars and contacts separately or together with IMAP. Map pairs per calendar or address book.
Nextcloud & WebDAV
File sync between Microsoft 365 (OneDrive) and WebDAV. Exactly one cloud side and one WebDAV side per plan.
Google Workspace Beta
Email, calendars and contacts via a service account. The connector is in beta and not released – no production use, no file sync.
From mapping to the report
Every run stays traceable – for internal projects and customer tenants alike.
Tenant & domains
Create a tenant, verify domains via DNS TXT and define allowed access modes.
Connections
Store profiles for Microsoft 365, IMAP or WebDAV. Credentials stay encrypted.
Dry-run
Map users, review the scope and test the run before productive data is written.
Sync & report
Follow live status, retry failed jobs and archive the completion report.
Built for operations, not just a one-off move
StackShift is multi-tenant, bilingual and designed for the security bar real customer projects require.
- Mandatory MFA via TOTP or email code. Sign-in without a second factor is not possible.
- Encrypted credentials per tenant, including AES-256-GCM.
- Audit logs and domain limits per tenant, including plan caps.
- UI in German and English, locale per tenant.
- Booking and billing via my.onesystems.ch. After that the portal is available.
Frequently asked questions
The answers teams typically need before the first sync.
What is StackShift?
StackShift is the multi-tenant migration and sync platform by OneSystems GmbH. It moves and aligns email, calendars, contacts and files between Microsoft 365 and self-hosted systems – for example IMAP, Mailcow, Stalwart or Nextcloud.
Instead of one-off scripts you work with auditable sync plans: connections live as profiles, users are mapped, a dry-run checks the scope, then syncs run with live status, retries and a completion report. That fits a one-time cutover as well as recurring reconciliation.
Each customer works in a dedicated tenant with their own domains, limits and roles. The UI is available in German and English; the locale can be set per tenant.
Which systems and data are supported?
Production-approved connectors are Microsoft 365 via Microsoft Graph (email, calendars, contacts and OneDrive), IMAP systems such as Mailcow or Stalwart, CalDAV and CardDAV for calendars and contacts, and WebDAV or Nextcloud for files.
Mail plans connect Microsoft 365 to Microsoft 365, Microsoft 365 to IMAP, or IMAP to IMAP. Calendars and contacts can run over Graph or DAV, including separately from mail if source and target need different logins. File plans mirror OneDrive and Nextcloud/WebDAV bidirectionally; each plan has exactly one Microsoft 365 side and one WebDAV side. Folder structure is preserved, with an optional WebDAV subfolder.
Google Workspace (email, calendars, contacts) is in beta and not released. There is no production use and no file sync via Google Drive.
Can I test before migrating?
Yes. Before productive data is written, a dry-run checks connections, user mapping and the expected scope. You see early whether domains are verified, profiles are correct and mapping is complete – without changing the target.
On the real run you follow progress live, retry failed jobs and get a completion report with an error list. Delta sync then transfers only changes since the last run instead of copying everything again. Retention and automatic deletion of run data follow the configured periods.
Is StackShift self-service, or does OneSystems run the migration?
Both. You book and pay for StackShift at my.onesystems.ch. With that account you open the portal and run sync plans, users and status yourself.
If you do not want to drive the migration yourself, OneSystems GmbH takes the project. You stay in the same portal at app.stackshift.ch and see the same reports.
How safe are credentials and operations?
Sign-in is only possible with multi-factor authentication, via a TOTP app or an email code. Nobody reaches the portal without the second factor. Sensitive credentials and sync options are stored encrypted per tenant, including AES-256-GCM.
Before a sync starts, domains must be verified via DNS TXT. Each domain has allowed access modes and plan limits, for example for mailboxes and concurrent jobs. Audit logs show who triggered what and when. OneSystems GmbH builds and operates the platform in Wattwil (SG), Switzerland.
How do I get started with StackShift?
New: book and pay for StackShift at my.onesystems.ch. Only then do you open the portal at app.stackshift.ch, set up MFA and create the first sync plan.
Existing customers go straight to the portal. Questions about plans or an assisted migration: OneSystems GmbH via the contact form or info@onesystems.ch.
Ready for the next stack shift?
Account and billing via my.onesystems.ch. The portal only with existing access.