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.
What the multi-account setup lets Cowork do
From one Cowork task, you can:
- search Outlook inboxes from several companies;
- build a briefing grouped by account;
- compare related threads across two tenants;
- check multiple calendars for conflicts;
- draft or send from the exact mailbox you choose;
- move, flag, or categorize a message in the correct account.
Carly keeps the Outlook connections separate and handles the routing underneath Claude.
Independent account or shared mailbox?
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 in the same tenant | Try Claude’s native Microsoft 365 connector first |
| A delegated mailbox or folder | Try the primary identity’s existing permissions first |
Claude can search shared mailboxes and delegated folders that the authenticated Microsoft identity already has permission to open. Carly solves the different problem: accounts that authenticate independently.
1. Give each Outlook account a tenant label
Create a simple map. For example (all addresses are fictional):
| Address | Role in Cowork |
|---|---|
fictional.claire.thompson@pepsi.com | Main Company |
fictional.claire.thompson@ford.com | Consulting |
Use both the full address and a clear role. Microsoft’s account chooser may display the same person’s name for both identities, while the tenant label makes the accounts easy to distinguish in a prompt.
2. Connect the first Outlook account to Carly
- Sign in at carlyassistant.com.
- Open carlyassistant.com/integrations.
- Find Outlook and click Connect.
- Sign in with the first Microsoft 365 account.
- Review and approve the requested permissions.
- Confirm the connected email address in Carly.
If Microsoft displays Need admin approval, ask the Entra administrator for that tenant to approve the connection, then finish authorization.
3. Add the second Outlook account and other tenants
Repeat the Outlook connection for every independent identity:
- Return to Carly’s integrations page.
- Select Outlook → Connect again.
- Choose Use another account if Microsoft preselects the first login.
- Sign in to the next Microsoft 365 account.
- Complete that tenant’s authorization.
- Verify the full address before connecting another.
Each account remains separate. Carly simply makes the named connections available through one account-aware tool layer.
4. 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.
5. Test each Outlook account read-only
Start with one mailbox at a time:
In
fictional.claire.thompson@pepsi.com, list the subject and sender of the five newest unread emails. Do not change anything.
In
fictional.claire.thompson@ford.com, find the newest message about Project Beacon. State the source account and do not draft or send.
Then test both accounts together:
Search both example Outlook accounts for meetings titled “Forecast” next week. Include the full account in every row and do not change either calendar.
When Cowork consistently returns the correct source account, move on to drafts and other actions.
6. Use this Outlook routing prompt
Paste this at the beginning of the Cowork task:
Treat
fictional.claire.thompson@pepsi.comas Main Company andfictional.claire.thompson@ford.comas Consulting. Always state the target account before changing data. Wait for approval before sends, moves, categories, or calendar changes.
Then keep the account in the action:
Draft the reply from
fictional.claire.thompson@pepsi.com. Do not send yet.
Move the vendor thread in
fictional.claire.thompson@ford.comto the Finance folder only.
Check both calendars, but create the approved event on the Main Company calendar.
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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