Aug 14, 2026

How to Connect Multiple Outlook Calendars to Codex

Codex has no first-party Outlook connector, which turns out to be an advantage here. Because calendar access arrives through whichever MCP server you register, the one-identity ceiling that stops the built-in connectors in other assistants is not something Codex imposes. Two tenants is a configuration problem, not a wall. Carly holds your Google calendars and every mailbox on both sides in the same place, so this setup covers the rest of what you own.

Codex is a coding agent, so the honest framing stays the same: this is for a developer who wants schedule context in a terminal. Recurring scheduling belongs in a workflow that runs without a session open.

1. Add your Outlook calendars to Carly

Sign in at carlyassistant.com.
Open carlyassistant.com/integrations.
Find Outlook Calendar, click Connect, and authorize the calendar.
Click Connect again for the next one, and keep going for as many calendars as you want.

Repeat for every additional tenant, choosing Use another account if Microsoft preselects the first login. Verify the full address after each authorization.

If Microsoft displays Need admin approval, that tenant’s Entra administrator approves the connection. On a client tenant you do not control, start this early rather than at the end.

Unlimited connected emails and calendars are included on the $35/month plan, so the third and fourth tenant cost nothing extra.

Carly connects to thousands of apps, so while you are on that page you can add your inboxes, files, CRM, and anything else you want Codex to reach through the same connector.

2. Register Carly as an MCP server

codex mcp add carly --url https://carlyassistant.com/mcp/

Servers added this way land in ~/.codex/config.toml at user scope. The manual entry is equivalent:

[mcp_servers.carly]
url = "https://carlyassistant.com/mcp/"

A trusted project can carry its own .codex/config.toml if you would rather scope the server to one repository.

Then authenticate:

codex mcp login carly

Complete the OAuth flow in the browser, signing in to the Carly workspace holding the calendars. Codex supports OAuth and bearer-token auth against remote HTTP MCP servers, so nothing goes into the config file as a secret.

Confirm it is live:

codex mcp list

Shared mailbox or separate identity?

Sort this first, because it decides whether you need any of this.

What you have	What it needs
Several calendars in one Microsoft 365 account	Nothing special, one authorization covers them
A shared or delegated calendar your account can already open	Usually the primary identity’s existing access
A second Microsoft 365 login	A separate authorization
Accounts in two tenants	A separate authorization per tenant

The common approach is a third-party MCP provider such as Composio, Merge, or Nylas, one server per account. Three tenants means three server entries, three OAuth apps to maintain, and nothing in the prompt vocabulary that distinguishes them, so the agent picks whichever loaded first.

Use the role in ordinary queries and the full address before anything that writes.

Address	Role
`[your-work-address]`	your work account
`[your-second-work-address]`	Consulting
`[your-personal-address]`	Personal

Third-party Outlook MCP versus Carly in Codex

Need	Per-tenant MCP server	Carly MCP server
Reach one calendar	Yes	Yes
Reach several tenants	One server per tenant	One server, all tenants
Address a specific account in a prompt	No shared convention	Yes, by email address
Find a time free across every account	No	Yes
Manage your own OAuth app and scopes	Often required	No
Add a fourth tenant later	New server entry	No config change
Keep the work running outside Codex	No	Yes

Free Zapier-style workflows; AI agents from $35/month. Connect it on the integrations page, or start with Outlook.

Quick fixes

Problem	Fix
Tools do not show up	Start a new Codex session after adding the server
`codex mcp login` never completes	Finish the browser OAuth flow, then rerun `codex mcp list`
Microsoft reopens the first account	Choose Use another account and reconnect
Microsoft shows Need admin approval	Ask that tenant’s Entra administrator to approve Carly
A shared calendar is missing	Confirm the primary identity can open it in Outlook
Events land on the wrong calendar	Use the full address and require confirmation before writes

Frequently asked questions

Does Codex have a native Outlook Calendar integration?

No. Codex reaches Outlook through the Model Context Protocol rather than a built-in connector, so what it can do depends on which MCP server you register.

How many Outlook calendars can this reach?

As many as you authorize in Carly. Codex connects to one server, so the tenant count is a Carly setting rather than a Codex one.

Is a shared calendar a second account?

No. A shared or delegated calendar relies on access already granted to a primary identity. Only a separate login or tenant needs its own authorization.

Can Codex find a time that works across two employers’ calendars?

Through a server that holds both, yes. Per-tenant servers cannot, because nothing in the setup lets one query span them.

Ready to automate your busywork?

Carly schedules, researches, and briefs you—so you can focus on what matters.

See what people say

"Before Carly, I relied on a Calendly link, but the whole process felt impersonal and not very professional. Carly changed that by handling all the back-and-forth, so I'm no longer stuck in endless email threads trying to line up schedules.

Now Carly reaches out to candidates, shares my real-time availability, lets them pick a slot, then sends a Zoom link and drops it straight into my calendar. She sends reminders to both of us before each call, which has significantly reduced no-shows and last-minute confusion.

On top of scheduling, Carly acts like a full executive assistant, sending me my schedule the night before so I can prepare for each call. It reminds me of the old x.ai assistant, but Carly is noticeably smarter, faster, and better suited to my healthcare recruitment business."

Gus Ibrahim, Founder & Director, IHR