Moving to Microsoft 365: what changes for your team

Moving mailboxes is the easy part and usually happens over a weekend. The work that takes planning is shared files, permissions and the habits people have built around the old server.

Most businesses we talk to aren't starting from nothing. They have an aging Exchange server in a closet, a file server with a mapped S: drive that everyone depends on, or a mix of personal Gmail accounts and a shared Dropbox that grew without a plan. Microsoft 365 can replace all of that, but a migration that only moves data from one place to another tends to carry the old problems along with it. A good migration is a chance to clean house.

Start with an inventory

Before anything moves, we write down what exists today: every mailbox, shared mailbox and distribution list; every file share and who uses it; the line of business applications that send email or read files from the server; and the devices people use to get work done, including personal phones.

This step always turns up surprises. A scanner that emails to an address nobody remembers creating. A folder called "Old Stuff DO NOT DELETE" that turns out to hold the only copy of the company's quoting templates. An accounting program that saves its database to a network share and will break if that share moves. Finding these before cutover is the difference between a quiet Monday and a long one.

Email: the easy part, done carefully

Email migrations are well understood. Mailboxes are copied to Microsoft 365 in the background over several days while people keep working. On cutover weekend we change the company's DNS records so new mail flows to Microsoft 365, run a final sync to catch anything that arrived in the meantime, and set up the records that help your mail stay out of other companies' spam folders.

The details that get missed are the ones outside the mailboxes: shared calendars, conference room bookings, email signatures, and printers or applications that send mail through the old server. We list those in the inventory and test each one after cutover.

Files: decide where things belong

Before a migration we map which folders belong in SharePoint, which belong in personal OneDrive, and who should have access to what. We turn on multi‑factor authentication before cutover, not after.

The rule of thumb is simple. Files that belong to one person and are shared occasionally go in their OneDrive. Files that belong to a team or department go in a SharePoint site, which also shows up as the Files tab in that team's channel in Microsoft Teams. Files the whole company needs, like policies, forms and templates, get their own site that everyone can read and only a few people can edit.

This is also when we untangle permissions. File servers that have been around for ten years usually have permissions set one folder at a time by whoever needed access that week. Rather than copying that tangle, we rebuild access around groups, so that when someone joins or leaves a department, one change covers everything they need.

For people who are used to a mapped drive, the OneDrive app can sync SharePoint libraries so they appear in File Explorer, just like before. Most users find that familiar enough that the change barely registers.

Security before cutover, not after

A new Microsoft 365 account is a target from the day it's created. Attackers try common passwords against every account they can find, and a single compromised mailbox can be used to send convincing invoice fraud to your customers. That's why multi-factor authentication is on before the first mailbox moves.

Alongside that, we turn off older sign-in methods that can't use multi-factor authentication, separate administrator accounts from everyday accounts, and set sensible rules for sharing files with people outside the company. None of this is visible to users once it's in place, and it's far easier to set up on an empty tenant than to retrofit later.

Choosing the right licenses

Microsoft 365 comes in several business plans, and the differences matter. Some plans include only the web and mobile versions of the Office apps. Others include the desktop apps. Business Premium adds device management through Intune and stronger security tools, which is usually the right choice for companies that handle customer data or have people working remotely.

Not everyone needs the same plan. A shop floor terminal that only checks email and a timecard can run on a lighter license than an estimator who lives in Excel all day. We match licenses to roles so you aren't paying for features nobody uses.

Phones, laptops and the little things

Phones are where most first-day questions come from. People need the Outlook and Teams apps, the Microsoft Authenticator app for sign-in approvals, and their old email account removed so they don't keep checking a mailbox that no longer receives mail. For company laptops, we can enroll them in device management so that settings, updates and security policies apply automatically, and a lost laptop can be locked or wiped remotely.

Habits take longer than data

The technology is usually the smallest part of the change. People who have saved files to the S: drive for fifteen years will keep looking for it. Someone will email a 40 MB attachment instead of sharing a link. A manager will ask why they can suddenly see everyone's calendar.

We handle this with short, practical sessions rather than long training days: where your files are now, how to share a link instead of an attachment, how to find something in Teams, and what to do when the Authenticator app asks you to approve a sign-in you didn't start. A one-page cheat sheet on each desk answers most of the rest.

The first Monday

On the first Monday we are on site or on call to help people sign in, find their files and set up their phones.

Most questions come in the first two hours. By the afternoon, things are usually quiet, and by the end of the first week people have stopped asking where the S: drive went.

After the move

A few things are worth doing once the dust settles. Microsoft keeps your data available, but its built-in retention isn't the same as a backup you control, so we back up mailboxes, OneDrive and SharePoint separately. We review license assignments after a month, since roles and needs become clearer once people are using the system. And the old server gets retired properly, with its data archived and its drives wiped, rather than left running in the closet "just in case".

Done this way, a move to Microsoft 365 leaves you with more than new email. You end up with a clear map of your files, cleaner permissions, better security and fewer servers to maintain.