Los Angeles · Chicagoland · Phoenix
Microsoft 365 Migration: Email, Files and Tenants, Moved and Secured
Moving to Microsoft 365, or between Microsoft 365 tenants, is mostly planning: where the mail and files are today, who holds the admin keys, which method fits, and when the DNS switch happens. BTI secures the tenant first, migrates in batches and keeps the old system available until everything is verified.
Call the IT team: Los Angeles 323-510-8003 · Chicagoland 312-492-2613 · Phoenix 480-272-8728
Free consultation
No cost. Business inquiries only. Already a BTI client? Use the dedicated support number assigned to your organization.
- ✓Over 40 years in business
- ✓400+ engineers
- ✓24/7 NOC/SOC
- ✓Microsoft Partner
- ✓Cisco Select Partner
- ✓ISO 27001 compliant governance, independently reviewed through the TAG ISO 27001 Compliance Program
Value engineer, scope, deliver, commission, then managed support
Value engineer, at no charge
Before anything moves, BTI reviews your Microsoft 365 licenses and the source system to find the lower-cost way to the same result: the right plans for each user, licenses you no longer need, and what can be retired instead of migrated.
Scope
Mailboxes, shared mailboxes, data volumes, file shares, DNS host, admin access and the migration method, in an itemized proposal.
Deliver
The tenant secured first, then mail and files migrated in batches.
Commission
Mail flow, DNS and email authentication (SPF, DKIM and DMARC) checked, MFA sign-ins, Outlook and phones tested, shared mailboxes and permissions verified, and admin access, licenses and settings documented in your name.
Managed support
After go-live, BTI can run Microsoft 365 with your team through co-managed IT (add people through IT staff augmentation), or for you through fully managed IT.
Finance 100% of your Microsoft 365 migration
A migration is a one-time project cost, and multi-year license packs often come with discounts that lower it. BTI can arrange 3.99% vendor financing for 100% of the project, including labor bundled with multi-year license packs and any equipment, for qualified buyers, subject to credit approval, through BTI's financing partners.
Where are you migrating from?
| Starting point | Method Microsoft supports | What to watch |
|---|---|---|
| Exchange Server 2016 or 2019 on site (support ended October 14, 2025) | Cutover, staged or hybrid migration to Exchange Online | Server health, public folders, shared mailboxes, archive files saved on PCs |
| Google Workspace | Gmail migration to Exchange Online; Google Drive to OneDrive and SharePoint through Migration Manager | Labels become folders, shared drives need a SharePoint plan, calendar sharing |
| Microsoft 365 bought through GoDaddy | Move of licensing and admin control into a tenant you control | Admin access, license timing, DNS records held at GoDaddy |
| Another Microsoft 365 tenant (merger, acquisition, divestiture) | Cross-tenant mailbox and OneDrive migration | One-time per-user license, domain move, Teams and SharePoint content |
| Hosted or older email (IMAP) | IMAP migration | Moves email only; calendars and contacts need a separate step |
| File server, Dropbox or Box | SharePoint and OneDrive through Migration Manager or the SharePoint Migration Tool | Permissions, long file paths, folders that should be cleaned up first |
Choosing the migration method
| Method | Best for | Trade-off |
|---|---|---|
| Cutover | Smaller Exchange organizations moving all at once. Microsoft supports up to 2,000 mailboxes but suggests 150 or fewer. | Everyone switches together, so the help desk needs to be ready for one busy morning |
| Staged | Larger organizations moving in batches | Two systems run side by side for a while |
| Hybrid | Organizations that need some mailboxes on site or a long, gradual move | More setup, and the on-site Exchange still needs care until it is retired |
| IMAP | Non-Exchange email systems | Email only |
| Cross-tenant | Mergers, acquisitions and divestitures | Per-user license and careful domain timing |
Source: Microsoft, "Ways to migrate multiple email accounts to Microsoft 365" and "Cutover migration" (learn.microsoft.com, checked October 25, 2026).
Security first, then mail
A migration is the easiest time to fix how Microsoft 365 is secured, because every account is being touched anyway. Before the first mailbox moves, BTI:
- Confirms who holds global admin, and moves admin access to named accounts with MFA.
- Turns on MFA for every user and sets sign-in rules in Entra ID.
- Sets email authentication records (SPF, DKIM and DMARC) so your mail is trusted and spoofing is harder.
- Plans backup of Microsoft 365 data, because Microsoft's retention is not the same as a backup you control. See backup and disaster recovery.
- Reviews who can share files outside the company.
How BTI runs the migration
Discover
Mailboxes, sizes, shared mailboxes, distribution lists, file shares, DNS host, licenses and admin access.
Secure the destination tenant
Admin roles, MFA, sign-in rules, email authentication.
Plan
Method, batches, licensing, the DNS change and a communication plan for staff.
Pilot
A small group moves first, including someone who will notice every problem.
Migrate in batches
Mail and files copied ahead of each cutover so the final switch is short.
Cut over
The MX record moves, a final sync runs, and Outlook and phones reconnect.
Clean up and document
Old system kept until verified, then retired. Admin access, licenses and settings documented in your name.
What goes wrong in Microsoft 365 migrations (and how we prevent it)
- DNS changed before mail is copied, so mail goes missing for hours. We copy first and change DNS last.
- Shared mailboxes and calendar permissions forgotten. They are in the inventory and the test plan.
- Archive files on PCs left behind. We find them during discovery and decide which to import.
- Phones and Outlook not reconnecting. Staff get a one-page "what to do Monday" note and help desk support.
- Old server switched off too early. It stays until the migration is verified.
- Licenses not assigned in time. Licensing is part of the plan, not an afterthought.
What drives the cost
- Number of mailboxes and how much data they hold.
- The source system (Exchange, Google, GoDaddy, another tenant, IMAP).
- How many files move to SharePoint and OneDrive, and how much cleanup they need.
- Licensing, including Microsoft's per-user cross-tenant license where it applies.
- After-hours cutovers.
Each item is a separate line in the proposal, and the whole project can be financed (see above). For licensing advice and Copilot, see BTI's Microsoft solutions.
Microsoft 365 migrations in your city
Los Angeles and Southern California
From Santa Fe Springs, BTI migrates firms across Los Angeles and Orange County, including multi-office organizations consolidating email after an acquisition. Call the LA IT team at 323-510-8003.
Chicagoland
From Downers Grove, BTI moves Loop and suburban organizations off on-site Exchange and Google Workspace. Call the Chicagoland IT team at 312-492-2613.
Phoenix and Tucson
Call the Phoenix team at 480-272-8728. Migrations are run remotely, with on-site help in Tucson delivered through contractors.
Why BTI for Microsoft 365
- Microsoft Partner with engineers who have run Exchange, Google and tenant-to-tenant moves.
- Security set before mail moves, not after.
- Over 40 years in business and 400+ engineers, counting BTI's own engineers plus the 24/7 NOC/SOC and help desk staff who work as part of BTI's team.
- ISO 27001 compliant governance, independently reviewed through the TAG ISO 27001 Compliance Program.
- Admin access, licenses and documentation in your company's name at the end.
Glossary: the terms in this page, spelled out
- M365 (Microsoft 365)
- Microsoft's subscription suite: Exchange Online email, Teams, SharePoint, OneDrive and Office apps. Examples: "We are moving email from GoDaddy to M365." "Store project files in SharePoint in M365."
- Tenant
- your organization's own instance of Microsoft 365, with its users, domains, data and settings. Examples: A tenant-to-tenant migration moves mailboxes after an acquisition. "Who holds the global admin for our tenant?"
- Cutover migration
- moving every mailbox from an on-premises Exchange server to Microsoft 365 in one batch. Microsoft supports up to 2,000 mailboxes this way but suggests 150 or fewer. Examples: A 60-person firm moves all mail over one weekend. After cutover, the MX record points to Microsoft 365.
- Staged migration
- moving mailboxes in batches over time instead of all at once. Examples: Finance moves first, operations the following week. Batches let the help desk support a smaller group at a time.
- Hybrid
- running on-premises systems and cloud services together, connected, during or after a migration. Examples: Hybrid Exchange keeps some mailboxes on-site while the rest move. A hybrid server setup keeps one app on-site and moves files to the cloud.
- IMAP (Internet Message Access Protocol)
- a standard way to read email on a server. Microsoft 365 can pull mail from IMAP systems during a migration. Examples: Mail from an older hosting provider is migrated over IMAP. IMAP migration moves email only, not calendars or contacts.
- MX record (mail exchanger record)
- the DNS setting that tells the internet where to deliver your email. Examples: Cutover happens when the MX record points to Microsoft 365. "Lower the DNS TTL before changing the MX record."
- DNS (Domain Name System)
- the internet's address book that turns names like btigroup.com into server addresses. Examples: "Who controls our DNS, the old IT company or us?" Email and website records live in DNS.
- SPF (Sender Policy Framework)
- a DNS record listing the servers allowed to send email for your domain. Examples: Adding Microsoft 365 to the SPF record before cutover. A missing SPF record sends your invoices to spam.
- DKIM (DomainKeys Identified Mail)
- a digital signature added to each outgoing email so receivers can check it really came from you. Examples: DKIM is turned on for the domain in Microsoft 365. A DKIM failure flags a forged message.
- DMARC (Domain-based Message Authentication, Reporting and Conformance)
- a DNS policy telling receiving mail systems what to do with mail that fails SPF or DKIM, and sending you reports. Examples: DMARC starts in monitor mode, then moves to quarantine. DMARC reports show someone spoofing your domain.
- MFA (multifactor authentication)
- signing in with a second proof, such as an app prompt, on top of a password. Examples: MFA blocks most stolen-password sign-ins. Turn on MFA before the migration, not after.
- Entra ID (Microsoft Entra ID, formerly Azure Active Directory)
- Microsoft's cloud identity service that controls who can sign in to Microsoft 365 and other apps. Examples: Conditional access rules in Entra ID block sign-ins from risky locations. New PCs join Entra ID instead of an on-site domain.
- SharePoint (Microsoft SharePoint)
- Microsoft 365's service for shared team files, sites and permissions. Examples: The S: drive becomes a SharePoint document library. Each department gets its own SharePoint site with its own permissions.
- OneDrive (Microsoft OneDrive)
- each user's personal file storage in Microsoft 365. Examples: Desktop and Documents folders sync to OneDrive. A departing employee's OneDrive is handed to their manager.
- Teams (Microsoft Teams)
- Microsoft 365's chat, meetings and team workspace app. Examples: Project channels in Teams store files in SharePoint. Teams Phone can replace desk phones for some users.
- EOL / EOS (end of life / end of support)
- the date a vendor stops selling, patching or supporting a product. Examples: Windows Server 2016 reaches end of support on January 12, 2027. A firewall past EOL stops getting security signatures.
Frequently asked questions
How long does a Microsoft 365 migration take?
It depends on the number of mailboxes, how much data each holds, where it is coming from and how many files move to SharePoint. BTI sets the schedule with you after the assessment and migrates in batches so people keep working.
Will we lose email during the migration?
Not when it is planned properly. Mail is copied to Microsoft 365 before cutover, the DNS change is scheduled, and a final sync picks up anything that arrived during the switch. The old system stays available until the migration is verified.
Can you migrate from Google Workspace to Microsoft 365?
Yes. Microsoft supports migrating Gmail to Exchange Online, and Google Drive content to OneDrive and SharePoint through Migration Manager. Calendars and contacts are included in the plan.
Our Microsoft 365 was bought through GoDaddy. Can we move it?
Yes. A Microsoft 365 subscription bought through GoDaddy is administered through GoDaddy. Moving to licensing you control is a planned project: BTI moves the licensing and admin control to you without losing mail.
What is a tenant-to-tenant migration?
Moving users, mailboxes and OneDrive files from one Microsoft 365 tenant to another, usually after a merger, acquisition or divestiture. Microsoft's cross-tenant mailbox migration needs a one-time, per-user Cross Tenant User Data Migration license.
Exchange Server 2016 and 2019 are out of support. What now?
Both reached end of support on October 14, 2025, so they no longer get security updates. Most small and mid-sized businesses move mail to Exchange Online in Microsoft 365, using a cutover, staged or hybrid migration depending on size.
Should our file server move to SharePoint?
Often, but not always. Shared team files usually fit SharePoint and personal files fit OneDrive. Very large files, some design and engineering data, and files used by on-site applications may be better on a server or in Azure. BTI decides folder by folder with you.
Do we need a managed IT agreement to migrate?
No. The migration is quoted as its own itemized project. After go-live you can keep running Microsoft 365 yourself, add co-managed IT, or have BTI manage it.
Tell us where your email lives today. An engineer will tell you the method, the risks and what it takes. The first consultation and the initial IT assessment conversation are free. The assessment scope is set on the initial engineering consult call.
Los Angeles 323-510-8003 · Chicagoland 312-492-2613 · Phoenix 480-272-8728
After go-live: keep your team in charge, add BTI where you need us.
Projects are where most relationships with BTI start. When the work is done, you choose what happens next: co-managed IT first, fully managed IT when it makes sense, and BTI back for your next project.
Co-managed IT
Your IT person or team stays in charge. BTI adds the help desk, a 24/7 NOC/SOC and engineers for the next project, with a written responsibility matrix. Need people rather than a service? Add an engineer or help desk coverage through IT staff augmentation. See co-managed IT
Fully managed IT
BTI runs IT end to end for one itemized monthly price, $60 to $290 per user per month. Managed IT · Itemized pricing
Security baseline
A cybersecurity assessment shows where the new environment stands before attackers or insurers look. Cybersecurity assessment
The first consultation and the initial IT assessment conversation are free. The assessment scope is set on the initial engineering consult call. Los Angeles 323-510-8003 · Chicagoland 312-492-2613 · Phoenix 480-272-8728
Already a BTI client? Use the dedicated support number assigned to your organization.