Microsoft 365 Migration Cost for a Small Business: What to Expect

Q: How is a Microsoft 365 migration usually priced?

Most providers charge a per-mailbox fee that covers migrating, verifying, and reconnecting each user, plus a fixed project fee for discovery, tenant setup, security baseline, and cutover. Microsoft licenses are billed separately as a recurring per-user subscription. The total rises with data volume, shared mailboxes and resource calendars, on-premise Exchange decommissioning, and any staged or hybrid approach that requires the two systems to coexist.

Q: What is the cheapest source to migrate to Microsoft 365 from?

Google Workspace and hosted IMAP accounts are generally the simplest and least costly sources because mail, contacts, and calendars move with standard tools. POP accounts look simple but often hide mail in local Outlook data files on each PC. On-premise Exchange and tenant-to-tenant migrations are typically the most involved because of server decommissioning, domain transfers, and Teams or SharePoint content.

Q: Do I still need a backup after moving to Microsoft 365?

Yes. Microsoft keeps the service available but does not provide a true point-in-time backup of your mailboxes and files. Deleted items age out of recovery, and ransomware that encrypts synced OneDrive files can propagate to the cloud. A third-party Microsoft 365 backup is a small per-user monthly add-on and should be included in every migration plan from the start.

Microsoft 365 migration cost for a small business is driven by four things: where your email lives today, how many mailboxes you have, how much data is in them, and whether you need a single-weekend cutover or a staged move. Most providers quote a per-mailbox fee plus a fixed project fee for planning, tenant setup, and cutover, with licenses billed separately by Microsoft. A clean move for a 10 to 25 person office is a modest one-time project; a messy one with an old on-premise Exchange server and years of PST files is not.

What drives Microsoft 365 migration cost?

Every migration quote we prepare for Treasure Coast businesses comes down to the same variables. Understanding them lets you compare proposals fairly.

Where you are coming from

Google Workspace (Gmail). Mail, contacts, and calendars move well with standard tools. Google Drive to OneDrive and SharePoint is the bigger job, because folder permissions and shared drives do not map one-to-one.
On-premise Exchange. Usually the most involved. The server may be old, patched irregularly, and holding years of mail. A hybrid or cutover migration requires careful preparation, and the server needs to be decommissioned properly afterward.
POP or IMAP hosting (GoDaddy, a web host, an old ISP account). Simple in principle, but POP mail often lives only on individual PCs in Outlook data files, and each one has to be found and uploaded.
Another Microsoft 365 tenant. Common after a merger or when a business separates from a parent company. Tenant-to-tenant moves involve domain transfers, identity re-creation, and Teams and SharePoint content, and take more coordination than a simple email move.

How many mailboxes and how much data

Per-mailbox pricing covers the labor of migrating, verifying, and reconnecting each user. Data volume affects how long the migration runs and whether it fits in a weekend. Twenty mailboxes averaging a few gigabytes is routine. Twenty mailboxes with fifteen years of attachments and shared mailboxes for every department is a different project. Shared mailboxes, resource calendars, distribution lists, and public folders each add work, so count them, not just people.

Cutover method

A cutover migration moves everyone at once, usually over a weekend, and is the simplest for small offices. A staged or hybrid migration moves groups of users over weeks and is used when a business cannot tolerate any disruption or has complex on-premise dependencies. Staged migrations cost more because they require coexistence between two systems.

What is usually included in a migration quote?

A competent proposal should list these explicitly:

Discovery: inventory of mailboxes, data, devices, and the applications that send email (scanners, practice-management systems, websites).
Tenant setup: domain verification, DNS records, security baseline, MFA enforcement, and license assignment.
Data migration of mail, contacts, calendars, and files, with verification.
Cutover: MX record change, Outlook reconfiguration on each PC, mobile device setup.
Post-migration support for a defined period, typically a week or two, when the questions come in.
Decommissioning of the old system.

What is usually not included: the Microsoft licenses themselves, which are a recurring per-user subscription; new hardware if old PCs cannot run a current Outlook; and any archive or backup you want of the old system.

Where do the surprise costs come from?

In our experience the surprises are almost never in the mailbox count. They come from things nobody mentioned during scoping.

PST files everywhere. Staff who have been archiving to local Outlook data files for years. Each one has to be located, checked, and imported, and some are corrupt.
Devices and applications that send email. The copier that scans to email, the alarm system, the website contact form, the practice-management software that sends appointment reminders. Each one authenticates to the old server and has to be reconfigured, and older devices cannot do modern authentication at all.
Domain and DNS access. The domain was registered by a former employee or a web designer who is no longer around. Recovering access can take days.
Old operating systems. A PC still on an unsupported version of Windows cannot run a supported Outlook and will need replacement.
Google Drive permission sprawl. Years of files shared with individuals and outside parties do not translate cleanly to SharePoint. Someone has to decide what the new structure looks like.
The extra tenant. Someone once signed up for a trial with the company domain, and now the real tenant cannot claim it until the old one is cleaned up.

A thorough discovery phase is worth paying for because it finds these before the weekend, not during it.

How long does a Microsoft 365 migration take?

For a typical small office, plan on one to two weeks of preparation, a weekend cutover, and a week of follow-up. Larger data sets are pre-synced during the preparation period so the final cutover only moves the last few days of mail. On-premise Exchange decommissioning and tenant-to-tenant moves can extend the timeline to several weeks.

How to keep the cost down without cutting corners

Clean house first. Have staff delete or archive what they do not need, and disable accounts for people who left years ago.
Give the provider complete information: every shared mailbox, every device that sends mail, every domain you own.
Choose the right license tier once. Downgrading and upgrading later creates churn.
Do not skip MFA and security baseline setup to save an hour. It will cost far more later.
Plan the migration outside your busy season. For seasonal Treasure Coast businesses that usually means summer, not January.

Do you need a separate backup after migrating?

Yes. This surprises many owners. Microsoft keeps the service running but does not provide a true point-in-time backup of your mailboxes and files. Deleted items eventually age out, and a ransomware event that encrypts synced OneDrive files can propagate to the cloud. A third-party Microsoft 365 backup is a small monthly add-on and should be part of every migration plan.

Getting a real number

The only honest answer to what it will cost your business is a short discovery call. We look at your current setup, count the moving parts, and give you a fixed-price proposal with the inclusions spelled out. MainSail Data handles Microsoft 365 migrations for businesses across Vero Beach, Sebastian, Fort Pierce, Port St. Lucie, and Stuart, and the same team supports you afterward. Call (772) 794-1194 for a free migration assessment.

Microsoft 365 Migration Cost for a Small Business: What to Expect Microsoft 365 · 5 min read