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1–5 inboxes or 40+ users: Migrate Gmail to Outlook for UK businesses

by | Sep 14, 2026 | AI

Administrator checking post-migration email errors

If you’re moving one or a few personal Gmail accounts, export a PST and import it into Outlook. If you’re migrating a business with multiple users, use the Exchange admin centre’s Google Workspace migration tool instead. Check Microsoft Learn for the exact prerequisites, generate an app password if 2-step verification is on, and back up everything before you touch a single setting.

TL;DR:

  • Migrating a single Gmail account to Outlook generally requires exporting a PST file and importing it into the new account, focusing solely on mail.
  • Business domain migrations benefit from using the automated Exchange admin center tool, which can transfer mail, calendar, and contacts, while managing batch size and throttling limits.
  • Proper preparation, including mailbox backups, enabling IMAP, verifying domain settings, and estimating mailbox size, is critical to prevent migration stalls.
  • Post-migration issues like label-folder mapping, throttling, and shared calendar permissions often require manual reconfiguration and validation before completing the move.
  • Complex, multi-user migrations with DNS cutovers should involve experienced support to minimize downtime and ensure accurate data transfer.
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Table of Contents

Manual PST/IMAP vs automated Google Workspace migration

The two routes solve different problems, and picking the wrong one wastes hours.

IMAP migration moves email only. It leaves calendars and contacts behind, which surprises people who assume “migrate my Gmail” means everything comes with it. The Google Workspace migration path, run through the Exchange admin centre, can carry mail, calendar and contacts together, and Microsoft documents both as native options with their own CSV formats and prerequisites.

  • Manual PST/IMAP: best for one to five personal accounts; takes a few hours; mail only.
  • Google Workspace migration (EAC): built for teams; takes a planning day plus a batch run; can include calendar and contacts.
  • Hybrid approach: some businesses export critical mailboxes manually while running the bulk of users through the automated wizard.

A single freelancer switching from a personal Gmail address rarely needs anything beyond PST/IMAP. A 40-person membership organisation moving its whole domain almost always benefits from the automated batch tool, or from bringing in a partner once the mailbox count climbs past what one IT person can babysit comfortably.

What to finish before you start the migration

Skipping prerequisites is the single biggest cause of stalled migrations. Work through this list first:

  1. Back up every mailbox you’re touching. Export a PST copy even if you’re planning to use the automated tool.
  2. Enable IMAP in Gmail settings, and generate an app password if 2-step verification is switched on.
  3. For business moves, confirm the domain is verified in Microsoft 365, allocate Exchange licences to every user, and prepare either a CSV of email addresses or a service account JSON for Workspace API access.
  4. Estimate total mailbox size and message count so you can size the migration window realistically.
  5. Write a short rollback and communication plan, including who gets notified if something needs pausing mid-run.

Pro Tip: Run a pilot migration on one non-critical mailbox first. It surfaces authentication errors and throttling limits long before they become a company-wide problem.

How do I move a personal Gmail account into Outlook?

For a single account, the fastest reliable path is exporting a PST from your current setup and importing it into the new one.

  1. Add the Gmail account to Outlook, or confirm IMAP is enabled in Gmail, and test that mail is syncing before you export anything.
  2. Export a PST file. In Outlook desktop, go to File > Open & Export > Import/Export, choose “Export to a file”, select Outlook Data File (.pst), and tick “include subfolders” so labels and nested folders come across intact. Microsoft’s own import guidance walks through this exact sequence.
  3. Remove the old Gmail account from Outlook. This avoids address conflicts when you add the new Microsoft 365 mailbox using the same profile.
  4. Add the new Outlook or Microsoft 365 account, then run File > Open & Export > Import/Export again, this time choosing “Import from another program or file” and pointing it at your PST.
  5. Verify the result. Run a few searches for recent and old emails, spot-check attachments opened correctly, and check that subfolders retained their structure.

Gmail’s own throttling can slow large exports. Gmail imposes a soft per-connection cap around 2GB, which matters if your mailbox runs into tens of thousands of messages. If calendar entries or contacts are missing after import, that’s expected. PST export only carries mail; for calendar and contacts, either export them separately from Google’s own tools or switch to the Google Workspace migration method described below.

How do businesses migrate Google Workspace to Microsoft 365?

For anything beyond a handful of mailboxes, the Exchange admin centre’s automated wizard is the practical default. It handles four configuration steps that would otherwise need doing by hand, and Microsoft recommends it specifically to reduce downtime and administrative complexity on business-wide moves. PowerShell remains the better choice for very large or repeatable migrations where you need scripted control over batches.

  • Prepare Google Workspace access. The automated wizard sets most of this up for you; the manual route needs a service account JSON with the right API scopes configured first.
  • Build your CSV. For IMAP-style bulk migrations, headers must read EmailAddress, UserName, and Password exactly as Microsoft’s template specifies, and the file can hold up to 50,000 rows and 10MB.
  • Create the migration endpoint in EAC, then create a migration batch pointing at either your CSV or the full Workspace mailbox list.
  • Monitor the batch status as it runs, and schedule a delta sync closer to your cutover date to catch anything sent during the main run.
  • Hold off on MX/DNS changes until the batch reports healthy completion. Switching DNS too early routes new mail nowhere useful.

Pro Tip: Domain-wide delegation with scoped OAuth avoids generating an app password for every single user, which matters a great deal once you’re past 20 or 30 mailboxes. This approach, detailed in Microsoft’s automated migration guidance, also allows higher concurrency and resumable runs controlled from the admin side rather than per user.

One limitation worth flagging early: native Microsoft tools move mail, calendar and contacts, but they don’t touch Google Drive. If file migration matters, that’s a separate project, and third-party tools built for broader scope exist, though they still operate within the same platform limits Microsoft sets.

Illustration of separate file migration scope

Fixing the errors that show up after migration

Most post-migration support tickets fall into a handful of predictable categories.

Gmail labels map to Outlook folders on a one-to-one basis, and that mapping often inflates message counts because a single email tagged with three labels can land in three folders. Plan destination mailbox quotas with that in mind rather than assuming a like-for-like size match.

  • Throttling: Gmail enforces IMAP connection limits, so large migrations should run in smaller concurrent batches or overnight to avoid failures.
  • Rules disabled: migrated inbox rules arrive switched off by default, so re-enable and test them individually rather than assuming they carried over working.
  • Shared calendars and delegation: these frequently need re-setting manually, since permissions rarely transfer cleanly between platforms.
  • Message-size limits: oversized attachments can silently fail to migrate; spot-check any mailbox known to hold large files.

Before calling the migration finished, run a validation pass: check a sample of recent and old messages, confirm folder structures match expectations, re-enable and test rules, run one final delta sync, and confirm DNS has fully propagated if you’ve cut over MX records.

When to do this yourself and when to call in help

Small personal moves, a handful of mailboxes, straightforward PST exports, these are genuinely DIY territory. Where it gets harder is multi-user domain migrations with DNS cutovers, mixed data types, and Drive content in the mix. That’s when a migration playbook and a second pair of hands pay for themselves, because a botched MX change can take a whole business offline for hours. Migration support covers planning, the actual execution, and post-migration validation, which is usually the stage most teams underestimate.

— Rob

Get your Microsoft 365 migration planned properly

A practical alternative to muddling through a domain-wide migration alone is available. Where the manual PST route works fine for one inbox, a multi-user move with DNS cutovers, license allocation, and calendar syncing genuinely benefits from someone who’s run the process before and knows exactly where it tends to break.

Cloud9

The planning, running of migration batches, result validation, and follow-up support are handled as part of comprehensive migration services. That matters most for established SMEs, membership organisations, and professional firms where a stalled inbox for half a day has a real cost. If your business is weighing up a Gmail to Microsoft 365 move and wants it done without the guesswork of a first attempt, get in touch through Cloud9’s cloud migration support page, or take a look at Microsoft 365 support if ongoing administration is the bigger concern.

Sources

FAQ

How do I migrate all my Gmail emails to Outlook?

Export your Gmail mailbox as a PST file using Outlook’s Import/Export wizard, then import that PST into your new Outlook or Microsoft 365 account. For calendar and contacts, use the Google Workspace migration path in the Exchange admin centre instead, since IMAP migration only carries email.

Why is Gmail no longer working in Outlook?

This usually comes down to authentication. Google now requires an app password or OAuth-based sign-in once 2-step verification is enabled, and an outdated password or disabled IMAP setting will block the connection entirely.

Can I convert my Gmail account to Outlook?

You can’t convert an account directly, but you can move all its data across. Export a PST for mail, or use the Google Workspace migration tool if you also need calendar and contacts carried over to a Microsoft 365 mailbox.

Should I sync my Gmail with Outlook?

Syncing works well as a temporary bridge while you check everything transferred correctly, but it’s not a permanent substitute for a full migration. Once you’ve verified the new mailbox, remove the old Gmail connection to avoid duplicate mail and address conflicts.