How to migrate Gmail to Microsoft 365 (formerly Office 365): a step-by-step guide

TL;DR: A Gmail to Microsoft 365 migration has two native paths. Microsoft's IMAP method moves mail only. No calendars, no contacts, no tasks. Microsoft's Google Workspace method adds calendars and contacts, but it's a separate, heavier setup and neither native path touches Google Drive. ShareGate Migrate handles Gmail, Google Calendar, Google Drive, and contacts in one tool, though platform limits still apply to any option.

Why companies move from Gmail to Microsoft 365

Your company just got acquired. Or your client did. Either way, there's a 90-day window to run a Gmail to Office 365 migration for 500 mailboxes, and someone picked you to make it happen.

You've got a hard deadline and a lot of mailboxes. Microsoft gives you free native tools to move email, calendars, and contacts. The question is which path fits your timeline, your team's bandwidth, and your tolerance for manual setup.

IMAP migration moves only mail folders. That's it. No calendars, no contacts, no tasks. If users need those, you're looking at the full Google Workspace migration path. Or a third-party tool that handles everything in one place.

This guide walks you through both options. You'll learn what native tools actually migrate (and what they leave behind), how to prepare your environment, and where ShareGate fits when native gaps create problems. Let's get into it.

Quick note on naming: Microsoft rebranded Office 365 to Microsoft 365 in 2020, so the two names mean the same suite. You'll see both here: "Office 365" where it matches what people search for, and "Microsoft 365," the current name, everywhere else.

IMAP-only vs. full Google Workspace migration: which one do you need?

An IMAP migration copies items from users' inboxes and mail folders to Exchange Online. That's the scope. Microsoft's documentation is clear: IMAP does not migrate contacts, calendar items, or tasks. If your users only care about email, IMAP gets the job done.

The "Perform a Google Workspace migration" path expands the scope. It moves Mail & Rules, Calendar, and Contacts. Microsoft's docs explicitly distinguish consumer Gmail mailbox moves from full Google Workspace content migration. These are different workflows with different prerequisites.

Most people searching for "Gmail migration" actually have Google Workspace accounts with calendars full of meetings and contacts they've been building for years. Someone starts with "let's just move the mail," and three weeks later there's a frantic Slack thread about missing calendar invites. If that sounds like a scenario you'd rather avoid, skip straight to the Workspace method. IMAP alone won't cut it.

How to migrate Gmail to Microsoft 365 with native tools

Microsoft gives you two native routes, and they're not the same. IMAP moves mail only. The Google Workspace method moves mail, calendars, and contacts. Pick the route before you prep, or you'll redo the connection work.

IMAP migration (mail only)

IMAP is the mail-only route, run from the Exchange admin center. Before you start any gmail imap migration office 365 workflow, check off these prerequisites:

• Global admin access: You must be a global admin in Microsoft 365 to run IMAP migration (Microsoft Learn).
• Mailboxes and licenses: Each user needs a mailbox AND a license that includes an Exchange Online plan before you can migrate email to it (Microsoft Learn).
• Domain verification: Verify you own your domain with a TXT record, or temporarily use the yourcompany.onmicrosoft.com domain (Microsoft Learn).
• Google-side prep: Account owners must create an app password, and users need 2-step verification turned on (Microsoft Learn).
• Migration CSV: Build a CSV with exact headers EmailAddress (A1), UserName (B1), Password (C1), up to 50,000 rows or 10 MB (Microsoft Learn).

Then add a migration endpoint with IMAP as the migration type and create a migration batch. You don't have to move everyone at once. Batch by department, priority, or risk (Microsoft Learn).

Google Workspace migration (mail, calendars, contacts)

This is the fuller route. It moves Mail & Rules, Calendar, and Contacts, and it doesn't use the IMAP app passwords or credential CSV. Instead you need a project creator role in Google Workspace, mail-routing subdomains, and users provisioned in Microsoft 365 before you migrate (Microsoft Learn). It runs three ways:

• Automated (Exchange admin center): the wizard sets up the Google connection for you.
• Manual (Exchange admin center): you create the Google service account and configure API access yourself.
• PowerShell: scripted, for larger or repeatable migrations.

Most teams start with the automated method, then move to PowerShell once they've got a repeatable workflow.

What native migration won't move

Native tools have boundaries, and knowing them upfront saves you from angry tickets the day after cutover. Here's what gets left behind when you migrate google workspace to microsoft 365 with Microsoft's built-in methods.

IMAP limitations: Calendar and contacts don't move. That's by design (Microsoft Learn).

Google Workspace path limitations (per Microsoft documentation):

• Room bookings won't be migrated.
• Shared calendars and event colors won't be migrated.
• Maximum 3 email addresses per contact.
• Gmail tags, contact URLs, and custom tags won't be migrated.
• Rules migrate but stay turned off by default. Verify them in Outlook before enabling.

Environment and policy constraints:

• Google Workspace migration is NOT available for Office 365 US Government GCC High or DoD (Microsoft Learn).
• Default single-message size limit is 35 MB (Microsoft Learn).
• Microsoft strongly recommends disabling all MRM and archival policies before migrating. Otherwise, items get flagged as "missing" (Microsoft Learn).
• Contacts and calendar throughput depends on your Google-side service account quota (Microsoft Learn).
• Large mailboxes stuck "Syncing" may be hitting Google bandwidth limits (Microsoft Learn).

Nothing kills project momentum like discovering these gaps on cutover day. Read the fine print before you commit to a timeline.

Gmail labels vs. Outlook folders: the problem nobody warns you about

Gmail uses labels. Outlook uses folders and categories. These aren't the same thing, and pretending they are causes real user-expectation problems during migration.

A single email in Gmail can carry multiple labels. When you migrate, those labels need to land somewhere. Map them to folders? You might create duplicate copies of the same message across multiple Outlook folders. That bloats the mailbox. Map them to categories? Everything sits in the inbox, and users complain their "folders" disappeared.

Users expect their Gmail labels to show up as Outlook folders. They don't understand why "Project Alpha" and "Q4 Reviews" aren't in the folder pane anymore. Set expectations before cutover and plan the mapping deliberately.

For noisy Gmail labels that don't need to migrate at all, you can use the -ExcludeFolder parameter in PowerShell (Microsoft Learn). If Gmail filter rules are causing more confusion than value, -SkipRules lets you leave them behind. Sometimes less is more.

How ShareGate handles a Gmail to Office 365 migration

Native tools make you stitch together separate workflows. IMAP moves mail only, and it wants per-user app passwords, 2-step verification, and a credential CSV. The Google Workspace method adds calendars and contacts, but it's a separate setup: a project creator role, mail-routing subdomains, and users provisioned before you migrate. Neither touches Google Drive. Visibility is limited, so you're left guessing what actually moved.

ShareGate Migrate takes a different approach. It moves Gmail, Google Calendar, Google Drive, and contacts in one tool. For the Gmail and Calendar migration, you connect once with a Google Workspace Super Admin using scoped OAuth. No per-user app passwords. No per-user consent prompts. No PowerShell to write or maintain.

What ShareGate brings to the move

• One tool for mail, calendars, Drive, and contacts: Dedicated Migrate features move mailbox content and Drive, instead of native's mix of IMAP, a Workspace method, and a separate Drive move.
• Assess before you move: See structure, ownership, and permissions before anything migrates. Fewer surprises on cutover day.
• Incremental copy: A delta pass moves only what's changed since your last sync. Cutover windows shrink because you're not re-copying everything.
• Progress tracking and reporting: Status down to each mailbox, calendar event, or file. Reports show what's moved, pending, and changed so you can prove the migration worked.
• No per-GB fees: Built into ShareGate Pro and Enterprise with no add-ons or usage caps. Pricing is predictable, unlike tools that meter by data volume.
• User mapping: Map users and recipients between Google and Microsoft 365, review a summary, then run or save for later.

Over 100,000 IT pros trust ShareGate for their Microsoft 365 projects. That's a decade of real-world experience informing how we handle edge cases.

What ShareGate won't do: ShareGate Migrate isn't a background sync service or a replacement for tenant design or governance. Post-migration actions validate and stabilize the target, not provide ongoing access governance. Platform-side limits (like Google quota throttling or Microsoft's 3-email-addresses-per-contact cap) still apply. We'd rather say that upfront than overpromise.

If native tool gaps are adding risk to your project, explore ShareGate's Google Workspace migration capabilities. For a detailed walkthrough, check out our step-by-step Google Workspace to Microsoft 365 migration guide.

After the migration: verify, cut over, and support users

Migration isn't done when the last mailbox shows "Completed." Verification, cutover, and user support decide whether your project lands as a success or a ticket backlog.

Run a pilot batch first. Test with a small group to estimate duration, batch sizes, and how many simultaneous connections your bandwidth can handle (Microsoft Learn).

Provision identities before migration. Every migrating user needs to be mail-enabled and licensed before their mailbox moves. Identity mismatches cause downstream failures that are painful to untangle (Microsoft Learn).

Verification checklist

• Check mail, folders, calendars, and contacts in the target mailbox.
• Review migrated Outlook rules before enabling them. They're disabled by default (Microsoft Learn).
• Spot-check users across departments. One success doesn't mean universal success.

DNS and cutover

Don't switch your domain or MX records until Gmail mailboxes are migrated. Update DNS and MX records at cutover to route new mail to Microsoft 365 (Microsoft Learn). Time this for low-traffic hours when possible.

User support

Prepare documentation and FAQs before cutover day. Users will ask where their labels went and how to find their contacts. A five-minute demo on finding contacts in Outlook saves hours of tickets.

Decommission the old Gmail environment only after the migration is confirmed complete and users are stable in Microsoft 365. Keep Google accounts read-only for two weeks if your licensing allows, then reclaim the licenses.