Migrating your emails, contacts, and calendar entries from your previous provider to Microsoft 365 represents a significant upgrade for most organisations. However, the process doesn’t conclude with the technical migration itself, comprehensive testing and verification are absolutely critical to ensure that no data is lost and that users can transition smoothly to their new environment.
Understanding the Migration Process
A successful migration to Microsoft 365 typically follows a carefully structured approach designed to minimise disruption whilst maximising data integrity.
Migration Phase One: Initial Data Transfer
On a scheduled cut-off date, all emails, contacts, and calendar entries up to that specific point in time are migrated to Microsoft 365. This creates a snapshot of your mailbox as it existed at that precise moment. It’s worth noting that this cut-off date is carefully coordinated with your organisation to ensure minimal impact on daily operations.
Testing Phase: Critical Validation
Following the initial migration, users must thoroughly validate their data against the cut-off date. This involves checking that everything has transferred correctly, from individual emails to complex folder structures and recurring calendar appointments. This phase cannot be rushed, it’s your opportunity to identify and flag any discrepancies before the final switchover occurs.
Final Switchover: Going Live
Once testing is complete and any identified issues have been resolved by your IT team, the organisation switches to Microsoft 365 as the primary mail service. At this point, DNS and MX records are updated, and Outlook becomes your main email platform across web, desktop, and mobile devices.
Why Testing Matters: The Stakes Are High
Even with the most robust migration tools and experienced IT teams, issues can arise during any large-scale data transfer. Missing emails, incomplete contact lists, or calendar discrepancies might seem minor individually, but collectively they can significantly impact productivity and business continuity.
Comprehensive testing ensures that:
- All emails and folders are present and accounted for, including those tucked away in custom folders or subfolders you may have created over the years
- Contacts and distribution lists remain intact, preserving the communication networks you’ve built within and outside your organisation
- Calendar events are correctly transferred, including recurring meetings, reminders, and any attendees or resources associated with appointments
- Folder hierarchies are preserved, maintaining the organisational structure you’ve developed for managing your correspondence
- Email rules and signatures transfer appropriately (where applicable to your migration type)
By identifying issues during the testing phase, you provide your IT team with the opportunity to resolve them before they affect your daily workflow. This proactive approach is far more efficient than attempting to reconstruct missing data after the final switchover has occurred.
Side-by-Side Comparison: What to Look For
Understanding what should transfer from your previous mailbox to Microsoft 365 helps you conduct more effective testing. Here’s a comprehensive comparison guide:
| Feature/Item | Previous Mailbox (Before Migration) | Microsoft 365 (After Migration) |
|---|---|---|
| Emails | All emails up to cut-off date | Should match exactly; verify Inbox, Sent Items, and all custom folders |
| Folders | Custom folders and hierarchical structure | All folders should be intact, visible, and maintain the same structure |
| Contacts | All contacts and distribution lists | All contacts and lists should be present with accurate details |
| Calendar Entries | All events, appointments, and recurring meetings | All events and meetings should transfer with correct times and attendees |
| Access Method | Old provider’s webmail interface or application | Outlook via Microsoft 365 (accessible via web browser, desktop application, or mobile app) |
| Reporting Issues | IT support via old system | Report any discrepancies to your IT team for prompt resolution |
Your Pre-Switchover Testing Checklist
Before your organisation completes the migration, it’s essential that you systematically verify your mailbox contents. Use this comprehensive checklist to ensure nothing has been overlooked:
| Item | Verified (✓) | Notes |
|---|---|---|
| All emails migrated correctly | ☐ | Check across all folders, not just Inbox |
| Folder structure intact | ☐ | Verify custom folders and subfolders |
| Contacts visible and accurate | ☐ | Check individual contacts and groups |
| Calendar entries complete | ☐ | Include past and future appointments |
| Recurring meetings present | ☐ | Verify series and exceptions |
| Sent items preserved | ☐ | Important for reference and compliance |
| Deleted items transferred | ☐ | If required by your organisation |
How to Conduct Your Verification
Checking Your Emails: Log in to Outlook (either via web browser or desktop application) and systematically browse through your Inbox, Sent Items, and all other folders. Pay particular attention to any custom folders you’ve created, as these can sometimes be overlooked during automated testing. Don’t just check that folders exist, open them and verify that emails are present and dated correctly relative to your cut-off date.
Verifying Your Contacts: Open the People or Contacts section in Outlook and review all entries. Check not only that contacts are present but that their details; email addresses, phone numbers, and any custom fields, have transferred accurately. If you use contact groups or distribution lists, verify these separately as they represent a different data structure.
Validating Your Calendar: Navigate to the Calendar tab and check for all scheduled events. Pay special attention to recurring meetings, as these can sometimes transfer incompletely. Verify that meeting invitations include all attendees and that any resources (such as meeting rooms) are still associated with the appropriate appointments. Check both past events (for historical reference) and future appointments (for operational continuity).
Reporting Issues: Communication Is Key
If you discover any discrepancies, missing items, or unexpected behaviour during your testing, it’s crucial to report these to your IT team immediately. When reporting issues, be as specific as possible:
- What is missing or incorrect? (e.g., “Emails from the Marketing folder dated between 1st and 15th March are missing”)
- When did you last see the item? (referencing the cut-off date helps tremendously)
- How critical is the missing data? (this helps IT prioritise their remediation efforts)
Your IT team will have tools and backup systems available to address most issues, but they can only help if they know what needs attention. Don’t assume that if something is missing for you, it’s missing for everyone, individual mailbox migrations can occasionally encounter unique issues.
Final Steps: Completing Your Migration Journey
Once you’ve thoroughly validated your mailbox and confirmed that everything has migrated correctly, notify your IT team that you’ve completed your testing. This feedback is essential, it allows them to track progress across the organisation and ensure that everyone is ready for the final switchover.
Your IT team will then:
- Update DNS and MX records to point to Microsoft 365
- Perform any final delta migrations (capturing emails that arrived after the initial cut-off)
- Officially switch over to Outlook as the primary mail service
- Decommission access to the old email system according to the agreed timeline
From this point forward, all new emails will arrive directly in Microsoft 365, and you’ll access your mailbox exclusively through Outlook.
In Summary
Careful testing and a methodical side-by-side comparison with your previous mailbox are absolutely essential for a successful migration to Microsoft 365. This isn’t simply an administrative formality, it’s your guarantee that years of correspondence, carefully organised contacts, and crucial calendar commitments make the journey intact.
By diligently following the checklist, conducting thorough verification, and promptly reporting any issues, you play a vital role in ensuring a seamless transition not only for yourself but for your entire organisation. The time invested in proper testing during the migration phase pays dividends in productivity, data integrity, and peace of mind once you’re fully operational on Microsoft 365.
Remember, your IT team is there to support you throughout this process. Don’t hesitate to reach out with questions or concerns; successful migrations are built on clear communication and collaboration between technical teams and end users.
