An IT migration isn't a weekend project. But with the right preparation, a complex undertaking becomes a manageable process. This checklist gives you an overview of the key steps – whether you're replacing Microsoft 365, moving your cloud infrastructure to Europe, or switching to Linux.

Phase 1: Inventory

Before you migrate anything, you need to know what you have. Sounds obvious – but it's regularly skipped.

Create a software inventory: What applications are in use? Document licenses, versions, and user counts.
Assess data volumes: How much data lives in OneDrive, SharePoint, Exchange, Google Drive, or AWS S3? Where are the duplicates?
Identify dependencies: Which systems depend on each other? Active Directory, SSO, API integrations, macros, plugins.
Document costs: Current license costs, cloud spending, support contracts – consolidate everything in one spreadsheet.
Analyze usage patterns: Which features are actually used? Often it's only 20% of the available functionality.
Identify stakeholders: Who needs to be involved? IT management, executives, works council, key users.

Phase 2: Goal Definition & Alternative Selection

What exactly should the migration achieve? Without clear goals, every decision becomes guesswork.

Define primary goal: Cost reduction? GDPR compliance? Digital sovereignty? End vendor lock-in? All valid – but the priority determines the strategy.
Evaluate open-source alternatives: Nextcloud instead of OneDrive, Collabora instead of Word Online, Element instead of Teams, Keycloak instead of Active Directory. Not everything fits every organization.
Run a proof of concept: Set up the new solution in a test environment and try it with real use cases.
Choose a hosting model: Self-hosted (on-premise), European cloud provider (Hetzner, IONOS), or managed hosting? Each model has trade-offs.
Set budget and timeline: Plan realistically with buffer. Migrations almost always take longer than expected.
Define rollback strategy: What happens if something goes wrong? Plan B must be in place before day one.

Phase 3: Data Migration Preparation

The actual data migration starts long before the first data transfer.

Clean up data: Remove outdated files, inactive accounts, and duplicates before migration. Less data = faster migration.
Plan folder structure: Copying the old structure 1:1 rarely makes sense. Now's the chance for a clean setup.
Document permissions: Who has access to what? This information is easily lost during migration.
Plan email migration: Exchange/Gmail to open-source mail servers is the most technically demanding data migration. Mailboxes, calendars, contacts, rules.
Create communication plan: Inform employees early. What's changing? When? Why? Where can they get help?
Develop training concept: Don't wait until the new system is live. Start early, begin with key users.

Phase 4: Pilot Phase

Never do everything at once. Always test with a small group first.

Assemble pilot group: 5–15 motivated employees from different departments. Mix of tech-savvy and less tech-savvy people.
Set up parallel operation: Old and new systems run simultaneously. Nobody loses access to their work.
Establish feedback process: Daily brief check-in during the first week, then weekly. What works? What doesn't?
Document and resolve issues: Every problem is an opportunity to improve the rollout for everyone else.
Make go/no-go decision: After the pilot phase, honestly assess: Are we ready for the broad rollout?

Phase 5: Gradual Rollout

Department by department, not big bang. Parallel operation continues.

Set rollout order: Which departments first? Usually start where the pain is greatest or complexity is lowest.
Execute data migration: Files, emails, calendars, contacts – transfer in the planned order. Verify checksums.
Conduct training: Before the switch date, not after. Hands-on, oriented around actual workflows.
Set up help desk: First weeks after switch: increased availability, short response times, patience.
Don't shut down old systems immediately: At least 2–4 weeks of parallel operation after switching. Safety net.

Phase 6: Follow-up & Optimization

A migration isn't a project with an end date – it's the beginning of a new IT era.

Cancel old licenses: Only after parallel operation has ended and all data has been verified. Watch the notice periods.
Measure success: Before-and-after cost comparison. Survey user satisfaction. What went well, what could improve?
Implement optimizations: Adjust workflows, set up automations, tune performance.
Ensure long-term support: Build internal expertise or sign an external support contract.
Update documentation: New systems, new processes, new contacts – document everything.

Special: Microsoft 365 Migration Checklist

The most common migration we support. Here are the specific steps for switching from Microsoft 365 to open source.

OneDrive → Nextcloud: Export files, document sharing permissions, set up Nextcloud client on all devices.
Outlook → Thunderbird / SOGo: Migrate mailboxes (IMAP/EWS), calendars (CalDAV), contacts (CardDAV). Transfer Outlook rules manually.
Word/Excel/PowerPoint → Collabora / LibreOffice: Check documents for compatibility. Adapt complex macros and templates.
Teams → Element / Mattermost: Export chat history (if possible), create new channels, test video conferencing quality.
SharePoint → Nextcloud + Wiki: Transfer intranet content, rebuild workflows, test search functionality.
Azure AD → Keycloak / FreeIPA: Migrate user directory, groups, SSO configurations. Most complex sub-migration.

Checklist too complex? We can help.

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