Microsoft 365 tenant rebranding

When a company changes its name — through rebranding, divestiture, or merger — the Microsoft 365 tenant has to follow. Some of the rebrand is straightforward; some pieces are surprisingly stubborn. A structured approach handles the project without leaving artifacts behind.

The scope of rebrand

A complete tenant rebrand touches:

• Domain name(s) — email addresses, SharePoint URLs.
• Tenant friendly name — what shows in admin centres.
• Branding — logos, colours, sign-in pages.
• User identities — User Principal Names (UPNs), email addresses.
• Resources — Microsoft 365 Groups, Teams, SharePoint sites with old names.
• Documents — content referring to the old name internally.
• External communications — partners and customers need to know.

It's a real project — typically months — not a one-day change.

Domain changes

The biggest single piece. The journey:

Add the new domain

• Add the new domain to the tenant (admin centre → Settings → Domains).
• Verify domain ownership via the TXT record Microsoft provides.
• Add necessary DNS records — MX, SPF, DKIM, DMARC, Autodiscover, Teams SIP.

The new domain is now available for use alongside the old.

Update users

For each user:

• Add the new SMTP address as a secondary alias.
• Change the primary SMTP to the new domain (Exchange will keep accepting mail to the old).
• Update the UPN if changing sign-in to the new domain.

Bulk via PowerShell:

Get-Mailbox | ForEach-Object {
    $newEmail = $_.Alias + "@newcompany.com"
    Set-Mailbox $_ -EmailAddresses @{Add=$newEmail}
    Set-Mailbox $_ -PrimarySmtpAddress $newEmail
}

Then update UPNs similarly with Set-User.

Update everything that references the domain

• Outlook autoconfiguration updates automatically via Autodiscover.
• Mobile devices may need reprofiling — communicate to users.
• External applications integrated via SAML / OIDC — verify SSO still works.
• Third-party SaaS that uses the email address — update mappings.
• DNS for SharePoint short URLs if you've configured them.
• Vanity URLs.

Decommission the old domain (eventually)

• Set up forwarding for the old domain to the new for a transition period (6–24 months).
• Communicate externally about the change.
• Eventually remove the old domain from the tenant.

Don't remove the old domain too quickly — external systems often have stale email addresses for years.

Tenant friendly name

The tenant friendly name (organisation name) appears in admin centres and some user-facing surfaces:

• Microsoft 365 admin centre → Settings → Org settings → Organization profile → Organization information.
• Update name and contact details.

This is a single change; takes effect within hours.

Branding

Update the visual identity:

• Custom theme in admin centre — new logo, colours, app launcher.
• Entra ID company branding — sign-in page logo, background.
• SharePoint home site / Viva Connections — corporate logo.
• Teams branded backgrounds and templates (if used).
• OME portal branding for external encrypted email recipients.

Each surface is independent; update them all for a consistent rebrand.

Microsoft 365 Group / Teams / SharePoint names

Groups, Teams teams, and SharePoint sites named after the old company need consideration:

• Groups can be renamed but the underlying SharePoint URL doesn't change automatically.
• SharePoint URLs can be changed via the admin centre site-URL update.
• Teams team names can be changed but display names don't update everywhere automatically.

For most groups, renaming is fine — the URL change is invisible to users who access via Teams or SharePoint navigation.

External communications

For partner-facing and customer-facing communications:

• Announce the change broadly before the cutover.
• Update email signatures organisation-wide.
• Update website and external content.
• Update contracts and legal documents (legal owns this).
• Press release if appropriate.

The external comms timeline is independent from the tenant-rebrand timeline; coordinate so users with new domain emails aren't sending to recipients who don't yet know about the change.

Operational considerations

• Pilot the change with IT and a small group first.
• Document the rebrand — what's changed, when, where.
• Help desk training — first-week post-rebrand has user questions.
• Long tail — third-party integrations, vendor relationships, old reports referencing the old name. Track and update.

For organisations rebranding, the tenant work is part of a broader project but worth treating carefully. Done well, the rebrand is invisible to users (and external partners) after the transition; done poorly, artifacts of the old name persist for years.