How to Migrate Gmail to Outlook in 2026 (Step-by-Step)

Migrating from Gmail to Outlook should be boring. In practice it has three failure modes that catch people out: the app-password requirement, the label-to-folder explosion, and Gmail's per-account IMAP throttle. Get those three right and the move is a non-event.

This guide walks the full process for a typical Gmail → Outlook (or Microsoft 365) migration and calls out the gotchas that show up in real mailboxes.

What you need before you start#

The single biggest source of failed Gmail migrations is starting without the right credentials in hand. Get these in place first.

• Admin access on the Outlook destination. Personal Outlook.com works, but Microsoft 365 with admin rights makes everything cleaner — you can use OAuth instead of a password, and you can run cross-mailbox validation.
• App password for every Gmail account being migrated. Each user-managed mailbox needs its own app password generated under the user's account. If you have Google Workspace admin, you can use a service account with domain-wide delegation instead.
• IMAP enabled in Gmail. It's off by default on new accounts. Settings → Forwarding and POP/IMAP → Enable IMAP. This takes 30 seconds per account but is required.
• A list of mailboxes with destination addresses, total message counts, and total size. This is your sizing data and goes straight into a CSV for batch import.

Step-by-step migration#

The seven-step walkthrough below moves a single Gmail account into Outlook. For multiple mailboxes, do step 1–2 for every user, then batch-import the rest.

1. Enable IMAP in Gmail

   Open Gmail, click the gear icon, then See all settings → Forwarding and POP/IMAP. Set IMAP access to Enable IMAP, scroll to the bottom and click Save Changes. Repeat for every Gmail account in the migration.

2. Generate a Gmail app password

   Go to myaccount.google.com/security. Confirm 2-Step Verification is on (it has to be, or app passwords are hidden). Click App passwords, give it a name like "Migration", and copy the 16-character password Google generates. Store it securely — you cannot retrieve it later.

3. Add Gmail as the source in Mailbox Taxi

   Open Mailbox Taxi, click New Migration, and pick Gmail from the source list. Enter the full Gmail address and paste the app password. Click Test Connection — you should see a list of folders within 5 seconds. If it errors with AUTHENTICATIONFAILED, the app password is wrong or 2-Step is not enabled.

4. Add Outlook as the destination

   Pick Outlook or Microsoft 365 from the destination list. For personal Outlook.com, enter the address and password. For Microsoft 365, sign in with OAuth — this avoids dealing with modern-auth headaches later. Test the connection.

5. Run a single-mailbox pilot

   Before importing your full CSV, run one mailbox end to end. Pick a mailbox you can open on the destination side. Confirm folders look right, that nested labels are nested, and that a recent message is present. Don't skip this step — it surfaces label-to-folder issues before they're spread across 200 mailboxes.

6. Batch-import the rest via CSV

   Prepare a CSV with source_email,source_password,destination_email,destination_password columns. Import it via Batch Migration → Import CSV. Mailbox Taxi will run all migrations in parallel up to the concurrency limit you set (4–8 is the sweet spot for Gmail).

7. Validate and cut MX records

   Once the dashboard shows all mailboxes complete, run a manual spot-check on 5% of the moved mailboxes. Change MX records to point at Outlook, wait for propagation, and run a final delta sync to catch any messages that arrived during cutover.

How Gmail labels translate to Outlook folders#

This is the part that surprises people most. Gmail uses labels: a message can carry many labels, and a label is essentially a tag, not a location. Outlook uses folders: a message lives in exactly one folder.

When a label-tagged message lands in Outlook, the migration tool has to make a choice. Mailbox Taxi copies the message into each label's folder, which preserves your ability to find it under any label but inflates the destination message count.

Two practical consequences:

• The Outlook destination will report more messages than the Gmail source. This is not a bug. It's the result of how labels map to folders.
• Storage usage on the destination is higher. If your destination mailbox is close to its quota, plan ahead — a 10GB Gmail account with heavy label use can land at 14–15GB on Outlook.

If multi-label inflation is a problem, configure Mailbox Taxi to migrate by inbox only and ignore labels. You lose label navigation, but the message count stays the same.

What about Google Workspace accounts?#

The steps above work for Workspace accounts too, but you have two better options if you have Workspace admin access:

1. Use OAuth with a service account. Instead of generating an app password per user, you create a service account in the Workspace admin console, grant it https://www.googleapis.com/auth/gmail.readonly, and let Mailbox Taxi authenticate per mailbox without bothering users. This is the right approach for migrations over 50 mailboxes.
2. Use Google Data Migration Service. Google's free tool can move mail to other Workspace accounts, but it's slower and offers no pause/resume. Worth considering only if your destination is another Workspace.

Troubleshooting common Gmail → Outlook errors#

The errors below are the ones we see week in, week out. Detailed fixes for each live on the troubleshooting hub; the short version:

• AUTHENTICATIONFAILED — App password missing, expired, or 2-Step Verification not actually on. Generate a fresh app password.
• Too many simultaneous connections — Gmail rate-limit. Drop your concurrency to 4 and resume.
• Folder UTF-7 conversion error — A Gmail label has non-ASCII characters Outlook can't accept verbatim. Mailbox Taxi will auto-rename and log the change.
• Message too large for destination — Outlook caps individual messages at 150MB. A handful of source messages with huge attachments will fail and need manual handling.
• Delegate access denied — You're trying to migrate a shared mailbox via a regular user account. Either grant the user "Full Access" on the source or run the migration from an admin context.

For a full reference of every error code we've documented, see the Gmail migration troubleshooting guide.

After cutover: tell users what to do#

The migration succeeds when users see their mail in Outlook without raising a ticket. A short, pre-written communication is the difference between a quiet week and a flood of support requests:

1. Remove the Gmail account from their phone's Mail app.
2. Add the new Outlook/Microsoft 365 account.
3. Re-enable any rules or out-of-office responses they had configured.
4. Re-share calendars with collaborators (Gmail calendar shares do not survive migration).

Send this message the morning after cutover, not before — users who try to add the new account before the MX records resolve get confused and call support.

Related migrations and reading#

If your migration is part of a broader move — for example a Google Workspace tenant being absorbed by a Microsoft 365 tenant — the complete migration guide covers the planning layer above this one. For the reverse direction, see Outlook to Gmail. For a deeper Workspace context, the Google Workspace migration guide is the next step.