Migration to Microsoft 365 from Exchange, Google Workspace or POP/IMAP hosting — pre-staged, rehearsed and cut over with no lost mail.
What usually goes wrong
Microsoft 365 migrations rarely fail technically. They fail on the details nobody inventoried.
The shared mailbox that three people in accounts rely on and nobody mentioned. The delegate permission letting an assistant manage a director’s calendar. The mail rule that files supplier invoices into a subfolder, which someone set up in 2019 and has never thought about since. The scanner in the corner that emails PDFs using an SMTP relay with a hardcoded password.
None of these are hard to migrate. All of them generate a furious Monday morning if they are discovered on Monday morning.
How we sequence it
Discovery. A full inventory: mailboxes and their sizes, shared mailboxes and who uses them, distribution lists, delegate and calendar permissions, mail rules, public folders, anything that sends mail through your server, and every device or application configured to use it.
Design. The identity decision is made here and it matters more than anything else. Cloud-only accounts, directory synchronisation from an existing on-premises directory, or federation — each has consequences for how sign-in works, and changing your mind after cutover is a project in itself.
Preparation and pre-sync. Tenant built, domains verified, licences assigned, security baseline configured. Mailbox content copied to the new environment and kept in sync while your existing system carries on as normal. This is the bulk of the elapsed time and none of it is disruptive.
Cutover. MX records switched in a planned window, final delta sync, clients reconfigured. For most businesses this is a weekend.
Aftercare. Elevated support for the first week, because the questions come on the first working day. The old platform stays intact until you confirm everything is right.
Do the security work during the move
A migration is the cheapest moment to get the security configuration right, because you are already touching every account.
MFA, conditional access, disabling legacy authentication, and email authentication records all cost far less to set up during the project than to retrofit later — retrofitting means a second round of change management with staff who have just been through one.
Migrations that defer this almost always leave it deferred.
What about the files?
Email and file migration are separate projects and it is worth resisting the urge to combine them. Both in one weekend doubles the surface area for something to go wrong, and file migrations have their own complications — permission structures that do not map cleanly, path length limits, and folder hierarchies built over fifteen years that probably should not be reproduced as they are.
If your file server is old and due for replacement anyway, doing both together makes sense. Otherwise, email first is the calmer route. SharePoint consulting covers the file side.