How to Connect Multiple Outlook Accounts to Claude Cowork
Yes, you can connect multiple Outlook or Microsoft 365 work accounts to Claude Cowork with Carly. Authorize each account in Carly, connect Carly to Claude once, and Cowork can work across several inboxes or tenants without repeatedly disconnecting Microsoft and signing in again. The same Carly account holds your Gmail inboxes and every calendar on both sides, so you set this up once for all of it.
1. Add your Outlook accounts to Carly
- Sign in at carlyassistant.com.
- Open carlyassistant.com/integrations.
- Find Outlook, click Connect, and authorize the account.
- Click Connect again for the next one, and keep going for as many accounts as you want.
If Microsoft displays Need admin approval, ask the Entra administrator for that tenant to approve the connection, then finish authorization.
Carly connects to thousands of apps, so while you are on that page you can add your calendars, files, CRM, and anything else you want Claude Cowork to reach through the same connector.
Each account remains separate. Carly simply makes the named connections available through one account-aware tool layer.
2. Add Carly to Claude Cowork
In Claude:
- Open Customize.
- Select Connectors.
- Click +, then Add custom connector.
- Paste
https://carlyassistant.com/mcp/. - Click Add and authorize Carly.
- In the Cowork task, open + → Connectors and enable Carly.
Anthropic’s custom connector instructions note that Team and Enterprise Owners may need to add the connector at the organization level before members can use it.
What the multi-account setup lets Cowork do
From one Cowork task, you can:
Check this before adding a second connection:
| What you have | Best setup |
|---|---|
| A second Microsoft 365 login from another company | Connect it separately through Carly |
| Two Microsoft 365 tenants | Connect and authorize each tenant through Carly |
A shared mailbox such as billing@ or support@ | Connect it to Carly as its own mailbox |
| A delegated mailbox or folder | Connect it to Carly, or use the primary identity’s existing permissions for read-only work |
Native Microsoft 365 versus Carly in Cowork
| Need | Claude’s native Microsoft 365 connector | Carly connector |
|---|---|---|
| Search one work identity | Yes | Yes |
| Search its shared mailboxes | Yes, with delegated access | Yes, according to account permissions |
| Use two independent Microsoft identities | Not in one native connection | Yes |
| Compare Outlook accounts across tenants | No | Yes |
| Send from a selected connected account | Yes when native write tools are enabled | Yes, with the connected account’s permissions |
| Run multi-account workflows | No | Yes |
Anthropic’s current Microsoft 365 setup supports write tools when an administrator enables them. Carly’s advantage here is not merely writing. It is making several independent accounts available to the same Cowork task. Carly offers free Zapier-style workflows; AI agents start at $35/month.
Quick fixes when an Outlook account is missing
| Problem | Fix |
|---|---|
| Microsoft opens the first account again | Choose Use another account and reconnect |
| Microsoft shows Need admin approval | Ask the Entra administrator for that tenant to approve Carly |
| A shared mailbox is missing | Confirm the primary account can open it in Outlook first |
| Carly is installed but absent from Cowork | Open + → Connectors and enable it for the task |
| Cowork uses the wrong tenant | Put the full address in the prompt and require source attribution |
| Claude cannot add Carly | Ask the Claude Owner to enable the custom connector |
Frequently asked questions
Can Claude Cowork connect multiple Microsoft 365 accounts natively?
Claude supports one authenticated Microsoft identity and the shared resources that identity can already access. Carly makes multiple independently authenticated Microsoft accounts available within one Cowork task.
Is a shared Outlook mailbox a second account?
No. A shared mailbox is accessed through permissions granted to your primary identity. If the second mailbox has its own login or tenant, connect it separately through Carly.
Does Carly merge the Outlook inboxes?
No. Every mailbox stays in its original Microsoft 365 account. Cowork can search across them, while Carly routes each draft, send, folder move, category, or calendar action to the account you name.
Related: What is Claude Cowork · Claude + Outlook · Claude for Microsoft 365 · Manage multiple email accounts with AI · Carly’s Outlook integration
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