How the migration actually runs
About six weeks from signature to the old account being cancelled. Here is each week, and what is asked of you in it — because “we handle everything” is what the last provider said.
Weeks 1–2
Inventory
I list every account, mailbox, shared drive and device, and find the things nobody remembers — the invoicing address that forwards somewhere, the calendar three people depend on.
From you: one hour, and access to the current admin console.
Weeks 2–4
Build and copy
Your hardware is set up and every service configured. Mail, files and photos are copied across while the old system keeps running and receiving. Nothing is switched yet, so nothing can break yet.
From you: nothing.
Week 5
Cutover
Mail delivery moves to your server on a Friday evening, after a final sync. Sending records are changed in advance and verified, which is the step that decides whether your mail lands in inboxes or in spam. Everyone gets a one-page note about what changed.
From you: people sign in once on each device.
Week 6
Watch, then cancel
The old provider stays live and paid for a full week. If anything is wrong we move delivery back the same hour — that is the point of paying for an overlap. You cancel when you are satisfied, and not before.
From you: tell me what feels wrong.
What does not come across
Said now rather than discovered in week five. Shared documents keep their content but not their comment history. Third-party apps connected to your old account need reconnecting once. Anything built on that provider’s own scripting has to be rebuilt, and I will tell you in week one if you have any.
If it goes wrong
Until you cancel the old account, going back is one change to your domain settings and an hour (DNS). After that it is a restore from backups you hold the key to. There is no point in the process where your data exists only in one place.
If the account you are leaving is Google Workspace or Microsoft 365, the page on leaving them covers what each one makes difficult on the way out.