Outlook calendar delegation

Outlook supports three distinct ways to share a calendar with someone else. They're often confused, and each has different capabilities and side effects. Knowing which to pick matters.

1. Delegate access

Delegate access gives someone the ability to act on your behalf in your mailbox — they can not only read your calendar but send meeting invitations as you, accept or decline on your behalf, see private items if you allow it, and read your inbox and tasks if you also delegate those.

Use case: executive assistant for an executive, where the assistant runs the calendar end-to-end.

Configured in Outlook → File → Account Settings → Delegate Access (classic) or in the new Outlook account settings. Permissions levels:

• Reviewer — read only.
• Author — create items.
• Editor — modify any item.

Delegates receive meeting requests on the delegator's behalf; replies sent by delegates show "Sent on behalf of."

2. Share permissions

Share permissions are simpler — share just the calendar with someone, with a defined permission level:

• Free/busy — they see when you're busy, but not what.
• Limited details — busy + meeting subjects.
• Full details — everything except private items.
• Editor — they can edit your calendar.

Use case: a peer who needs to see your availability, a project team that should see each other's calendars.

Configured per calendar from the calendar's right-click menu → Share calendar.

3. Shared calendars (Microsoft 365 Group)

A Microsoft 365 Group has its own shared calendar that all group members can see and modify. Use case: a team's "team calendar" — vacations, key dates, on-call rotations.

Distinct from personal-calendar sharing — the group calendar is its own object, not anyone's personal one.

When to use which

| Need | Option | | --- | --- | | Assistant runs an executive's calendar | Delegate access | | Peer needs to see when you're busy | Share permissions, Limited details | | Team needs a shared calendar for events | Microsoft 365 Group calendar | | Project needs an audit-friendly events log | Group calendar | | Reception needs to book exec time | Delegate access |

Common operational issues

• Cached mode and shared calendars — large shared calendars cached on disk grow OST files. Configure cached mode to skip caching shared calendars when not needed.
• New Outlook for Windows — delegation and shared calendars work, but the UI is slightly different from classic Outlook; verify with users before migration.
• Private items — by default, delegates see free/busy of private items; they can be granted access to see content if needed.
• Permissions inheritance — sharing a top-level calendar doesn't automatically share sub-calendars in the same mailbox.

For organisations with many executive-assistant relationships, document the delegation pattern — who is delegate for whom, with what level. Audit periodically; delegations linger after staff changes.