Migrate Google Workspace to Fastmail (2026 Guide)

Migrating away from Google Workspace usually isn't a cost decision — it's a values one. Fastmail attracts people who want fewer trackers, predictable pricing, and a vendor whose business model is just selling email. The mechanical work to get there is straightforward in theory: both sides speak IMAP, Fastmail has a built-in importer, MX cutover is standard. The traps are in the details: Gmail's labels-to-folders conversion changes storage math, Google throttles IMAP aggressively, and the contacts and calendar layer needs its own plan. This guide walks the path with the gotchas in their right places.

Labels vs folders: the fundamental shift#

Gmail stores each message once and applies one or more labels. Fastmail stores each message in exactly one folder. When you migrate, every label on a message becomes a folder, and the message is copied into each one.

The practical consequences:

• Storage will be larger on Fastmail than on Gmail. A 30 GB Gmail mailbox where users heavily use labels can become 40–60 GB on Fastmail.
• Search across "labels" on Fastmail means searching across folders, which works but feels different to users coming from Gmail's instant label filtering.
• INBOX is no longer a label that can coexist with other labels. On Fastmail, a message is either in INBOX or in some other folder, not both.
• The "All Mail" pseudo-label on Gmail is the deduplicated message store. On Fastmail, the equivalent is "search across all folders".

Decide before migration: do you replicate every label as a folder, or do you flatten some labels into a single archive folder? Most users prefer flattening labels that have under 20 messages and replicating those with high message counts.

Setting up Fastmail#

Get the destination ready before touching the source.

Create Fastmail accounts#

Sign up for Fastmail at fastmail.com. The Business plan supports custom domains and shared resources; the Individual plan handles single-user migrations. Pricing is published — current rates are around $5/user/month for the Standard plan with 30 GB storage, $9/user/month for Professional with 100 GB. Check fastmail.com for current rates.

Create user accounts matching the Workspace addresses. Fastmail uses email-address-style usernames natively, so user@yourdomain.com is both the login and the primary address.

Verify the domain#

In Fastmail's admin (Settings → Domains), add your domain. Fastmail provides verification records — a TXT record at the apex and MX records for the eventual cutover. Add the TXT now to verify ownership; leave MX pointed at Google for now.

Plan storage#

For each user, check their Gmail storage usage at admin.google.com → Reports → User reports → Apps usage. Multiply by 1.3–1.6× to estimate Fastmail storage need after labels become folders. If anyone is going to exceed Fastmail's per-user storage, upgrade to a tier with more storage before migration.

Google Workspace prep#

Enable IMAP for each user#

In the Workspace admin console, check that IMAP is enabled (Apps → Google Workspace → Gmail → End User Access → POP and IMAP access). It's enabled by default, but some hardened tenants have it disabled.

Per-user, IMAP can also be toggled in Gmail Settings → Forwarding and POP/IMAP. Verify it's on for each migrating user.

App passwords#

Workspace users with 2FA enabled (which should be all of them) need an app password to authenticate via IMAP. Each user generates their own at myaccount.google.com → Security → App passwords. Or, if your tool supports OAuth, you can skip app passwords entirely and authenticate via OAuth scopes.

For a refresher on what app passwords are and how they work, our app password glossary entry covers the basics.

If your Workspace tenant has disabled user-managed app passwords (Admin console → Security → Less secure apps), either re-enable temporarily or use OAuth-based migration.

Lower DNS TTL#

24 hours before MX cutover, drop your MX record TTL to 300 seconds in whatever DNS provider hosts your domain. Standard practice for any migration.

Choosing your migration tool#

Fastmail's built-in importer#

In Fastmail (Settings → Import), choose Gmail/Google Workspace. OAuth-authenticate the source account, pick which labels/folders to import, and Fastmail runs the migration server-side. Free with any Fastmail account, no software to install.

Limitations: works one mailbox at a time (per Fastmail account), can be slow (10–15 GB per day per mailbox), error reporting is minimal, no delta sync after the first pass.

Good for: single-user migrations, organizations with under 10 users where time isn't critical, anyone who values not installing migration software.

Desktop IMAP tool#

A local tool authenticates to Gmail (via app password or OAuth) and Fastmail (via app password) and runs IMAP-to-IMAP migration. Mailbox Taxi is built for this — desktop-first, with concurrency control, detailed per-message logging, and resumable syncs.

Desktop tools beat Fastmail's importer for:

• Multi-user organization migrations where you need parallel execution.
• Detailed logging for compliance audits.
• Delta syncs at the end to catch stragglers.
• Custom label-to-folder mapping (the importer flattens, a desktop tool can be configured).

For a deeper look at the IMAP protocol mechanics underlying both approaches, our IMAP protocol glossary covers the relevant background.

Hybrid#

Fastmail's importer for the bulk, a desktop tool for delta and validation. Free bulk, controlled delta.

Step-by-step#

1. Pilot two mailboxes

   Pick one user with heavy label use and one with minimal labels. Run end-to-end. Validate:

   • Folder structure on Fastmail matches your label-to-folder plan.
   • Sent items are in the Sent folder, not duplicated across labels.
   • All Mail is excluded (verify by checking total message count vs sum of folder counts).
   • Storage on Fastmail is what you expected.

   If storage is unexpectedly large, you're probably importing All Mail. If folders are missing, your label-to-folder map may be filtering them out incorrectly.

2. Capture credentials securely

   For each user, get either an app password or OAuth tokens for Google. App passwords are easier to share (admin can generate them on behalf of users via password reset, then issue app passwords). OAuth requires the user to authenticate interactively.

   Store everything in a password manager. Document which method each user is using so you can troubleshoot consistently.

   On the Fastmail side, generate an app password per user from their Fastmail account settings. Migration tools authenticate to Fastmail with the app password, not the master password.

3. Run the bulk pre-sync

   48 hours before MX cutover, kick off the bulk migration for all mailboxes. Cap concurrency at 4–5 threads per mailbox; Gmail throttles harder than people expect.

   Common Gmail throttling signals:

   • Too many simultaneous connections — drop concurrency.
   • Lookup failed on labels — Gmail is rate-limiting label queries. Slow down.
   • OAuth2 token expired (if using OAuth) — refresh tokens and resume. Most tools handle this automatically.

   For a 25-user organization with 15 GB average mailbox sizes, expect 36–60 hours of bulk sync.

4. Cut MX records to Fastmail

   At your cutover time, update MX records at your DNS provider to Fastmail's published values. Fastmail's MX records are typically:

   • Priority 10: in1-smtp.messagingengine.com
   • Priority 20: in2-smtp.messagingengine.com

   (Verify the exact records in your Fastmail admin console — always copy from the source.)

   Verify propagation with dig MX yourdomain.com @8.8.8.8 and dig MX yourdomain.com @1.1.1.1. Send a test message from external accounts.

5. Run the delta sync

   48 hours after MX cutover, run a delta against each Google Workspace mailbox. Any mail that arrived at Workspace during the propagation window will be on the Google side; the delta pulls it across.

   If you set up a Workspace-to-Fastmail forwarder before cutover (in each user's Gmail settings → Forwarding), the delta will be small because mail was forwarded in real-time.

6. Import contacts and calendars

   Per-user:

   • Google Contacts → Export → vCard. Then Fastmail → Contacts → Import → upload vCard.
   • Google Calendar → Settings → Export. Then Fastmail → Calendar → Import → upload .ics files.

   This is genuinely a per-user task and is often easier if users do it themselves. Or, log into their Google account with their app password (or have them export and email you the files) and do it from their Fastmail account.

7. Update SPF, DKIM, DMARC

   SPF: v=spf1 include:spf.messagingengine.com ~all. Remove include:_spf.google.com.

   DKIM: in Fastmail admin (Settings → Domains → your domain → DKIM), enable DKIM and copy the CNAME records into your DNS. Fastmail manages key rotation.

   DMARC: keep your existing record or update the policy. If you had p=none before, leave it for a week to see Fastmail's effect on report volume before tightening.

8. Decommission Google Workspace

   After 30 days of clean operation on Fastmail, cancel the Workspace subscription. Don't rush — 30 days catches users who realize they're missing something and need to retrieve it from the source.

   Before cancelling, export each user's data via Google Takeout as a final backup. This includes mail, contacts, calendars, Drive files, and anything else. Store the archives somewhere you'll find them later.

Common failure modes#

OAuth2 token expired#

If you're using OAuth, tokens expire periodically. Most tools handle refresh automatically; some don't. If your tool stalls with this error, manually re-authorize the source.

Too many simultaneous connections on Gmail#

Drop concurrency to 2–3 threads per mailbox. Gmail's per-account limit is around 10 simultaneous IMAP connections, but practical safe concurrency is lower.

Storage exceeded on Fastmail mid-migration#

If the destination runs out of quota, the migration halts. Upgrade the Fastmail plan and resume. To avoid this, calculate storage need in advance with the 1.3–1.6× label-multiplier.

Folders not appearing on Fastmail#

If labels nested under other labels on Gmail (e.g., Projects/Q1/Reports) aren't showing up on Fastmail, your tool may be flattening or filtering. Check the label-to-folder mapping settings.

Duplicate messages across folders#

If you imported [Gmail]/All Mail, you'll have duplicates. The fix is non-trivial — easier to start over without All Mail than to deduplicate after the fact.

Sent items in two places#

Gmail's "Sent Mail" label is a special label that also appears as a folder. If both get imported, you'll have sent mail in Sent and in some other folder. Your tool should exclude one or the other. Default is usually to import only Sent.

Comparing to other destinations#

For organizations weighing privacy-focused alternatives, the Workspace to ProtonMail path is the next step in privacy-tier upgrade and has different mechanics (ProtonMail Bridge for IMAP access on the destination).

For the reverse direction — Fastmail to Gmail — the Fastmail to Gmail walkthrough handles label-from-folder reconstruction.

For organizations not yet committed to Fastmail and still weighing Workspace migration paths broadly, the Google Workspace migration guide covers destinations in more detail.

Validation#

Per-user:

• Folder count on Fastmail matches the label-to-folder map count.
• Message counts per folder are within expected ranges.
• Sent items in the Sent folder.
• INBOX has expected messages and only INBOX-labeled messages.
• Mobile clients connect to Fastmail successfully.

Per-tenant:

• SPF, DKIM, DMARC all updated and validating.
• All aliases recreated.
• Test mail flows correctly from external Gmail, external Outlook.com, and external Fastmail accounts.

When validation passes, you're done. Wait 30 days, take a final Google Takeout backup, then cancel Workspace.