Exchange Online guides

How to add an email domain to Microsoft 365 without downtime: verification, accepted-domain type, SPF, DKIM, DMARC before MX, and the mail-flow traps.

Business Premium vs Microsoft 365 E3: Premium wins on security for less money, E3 wins on mailboxes, Windows, and scale. How to choose, and how to mix them.

How to share calendar free/busy between Microsoft 365 tenants — organisation relationships and modern alternatives.

How hybrid Exchange works — connecting on-prem Exchange Server with Exchange Online, what the wizard actually does, and the path off the last server.

How mail moves into and out of Exchange Online — connectors, transport rules, and hybrid routing.

How room and equipment mailboxes work — provisioning, booking, and admin pitfalls.

What breaks in a Teams Rooms fleet when a certificate expires — Wi-Fi, 802.1X, proxy roots, hybrid Exchange — how to tell which, and renewing fleet-wide.

How to block a compromised Microsoft 365 account in ten minutes: disable sign-in, revoke sessions, reset password and MFA, kill inbox rules and forwarding.

How to convert a user mailbox to a shared mailbox in Exchange Online, when it's the right leaver move, the 50 GB and hold rules, and removing the licence.

How to create a DLP policy in Microsoft Purview for card and personal data: locations, sensitive info types, rules and actions, simulation mode, enforcement.

How to create a retention policy in Microsoft Purview: static or adaptive scope, locations, retain-then-delete settings, and rolling it out without surprises.

How to offboard a user in Microsoft 365: block sign-in, revoke sessions, handle the mailbox and OneDrive, wipe devices, remove licences, delete on schedule.

How to put a mailbox on litigation hold in Exchange Online: licence check, enabling the hold with a duration, what it preserves, and releasing it correctly.

How to restore a deleted user in Microsoft 365 within the 30-day window: admin center and Graph routes, UPN conflicts, what comes back, and after 30 days.

How to set up DKIM signing for a custom domain in Microsoft 365: the two CNAME records, enabling it in Defender, key rotation, and checking headers.

How to architect network traffic for Microsoft 365 — local egress, optimisation, and the network connectivity principles Microsoft publishes.

What Defender for Office 365 adds on top of EOP — Safe Links, Safe Attachments, AIR, attack simulation — plus Plan 1 vs Plan 2 and the settings worth tuning.

How to move an address from a shared mailbox to a distribution group, or back, without dropping mail — what happens to history, and when a Group is better.

A practical migration playbook for moving from Google Workspace to Microsoft 365 — workloads, tools, and pitfalls.

How to move mailboxes from Exchange Server to Exchange Online — the migration types, hybrid deployment, and the realistic plan.

New Outlook vs classic Outlook on Windows: what actually changes, what still doesn't work, and how to run the migration without a user revolt.

How OME works under the hood — encryption flow, branding, custom templates, and the recipient experience.

How classic Outlook caches mailbox data locally — what an OST file is, when to use cached mode, and the modern alternatives.

How Focused Inbox separates important mail from the rest, and what happened to its predecessor Clutter.

How Exchange Online decides which addresses a mailbox answers to: proxy addresses, primary SMTP, UPN vs email, sending from aliases, and hybrid gotchas.

What must be true before the last Exchange server can go: recipient management, relay, public folders, management-tools-only, and the removal sequence.

Shared mailboxes are mailboxes multiple people can monitor. Here's how they differ from groups, distribution lists, and personal mailboxes.

What Exchange Online is: Microsoft 365's cloud email and calendaring, how it fits the platform, the security and compliance layers, and running it well.