106 mailboxes. 848 gigabytes. One 30-day window.

Our client is the holding company behind a collective of 15+ creative agencies. When it moved from Office 365 to Google Workspace, nothing was allowed to go missing — not a delegate, not a distribution list, not a decade-old thread.

Client: Parent entity of a 15+ agency creative collective
Scope: Tenant-to-tenant: Exchange Online → Gmail, plus groups, delegates & forwarding
Window: 30-day cutover window, planned against measured throughput
Tooling: 15 purpose-built PowerShell scripts · GAM · MoveBot

106licensed mailboxes, ~848 GB of mail inventoried

119Google Workspace accounts provisioned, 27 of them net-new

3,467group memberships rebuilt across 53 groups

99.6%coverage recreating a 2,104-member cross-agency list

Step one: know everything before you move anything

Migrations fail on the things nobody wrote down. So before a single message moved, we built the written-down version: fifteen PowerShell scripts that interrogated the Office 365 tenant from every angle.

Every mailbox, sized and dated

Full inventory of mailbox sizes and last logins — which is how you find the 86 GB mailbox that will quietly become your schedule's long pole.

Every delegate and forward

Access delegation mapped 1:1 to Gmail delegation, and forwarding audited across all three places it hides: mailbox settings, inbox rules, and org-wide transport rules — with ~78 external forwards flagged for security review before cutover.

Every group, reconstructed

53 groups and roughly 3,467 memberships rebuilt on the Google side — including membership reconstructed from audit logs as of a fixed cutoff date, and ownerless groups traced back to real humans.

Planning against physics, not optimism.

Microsoft throttles mailbox exports hard, and no vendor tool can talk its way past that. We did the throughput math up front — per-mailbox rate limits, best/expected/worst-case durations — and sequenced the two biggest mailboxes to start on day one, hour one. The 30-day promise was built on arithmetic, not hope.

Diagram of a cloud migration: Microsoft 365, Dropbox, Box, and Slack tiles with documents and mail flowing along amber lines into a glowing Google Workspace tile — Here the source was Exchange Online — but the playbook is the same whatever you're leaving: mail, files, and groups moved by an unattended copier while people keep working, and old-platform access wound down per-user without breaking the pipe the migration runs through.

The edge cases are the job

A 2,104-member external list

The collective-wide distribution list reached people at every agency in the network. It was rebuilt to 99.6% coverage, with the handful of rejects individually accounted for — not shrugged off.

Ghost accounts and orphan owners

GUID-named mailboxes, groups whose owners had left years ago, names on lists that matched no user — each one chased to a human answer instead of migrated as garbage.

Coexistence without chaos

Teams and Outlook were wound down in a controlled, reversible way — per-mailbox, keeping mail flow and the migration pipe intact — so the org changed platforms without a hard stop.

Guardrails on the operator, too

All tooling ran through a tenant-isolated wrapper so commands could not accidentally touch the wrong Google tenant. When you administer more than one company, that's not paranoia — it's table stakes.

Why this matters to you

Every number on this page came from an inventory script, not a slide. That's the difference between a migration plan and a migration guess — and it's how your company's move gets promised in days, delivered without drama, and documented well enough that the next IT person silently thanks us.

Facing a migration everyone's afraid to start?

Email, files, identity, DNS — we've done the scary weekend. First call is free.

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