How to Connect Multiple Outlook Accounts to Claude
Claude’s Microsoft 365 connector authorizes one account, but you can still reach several mailboxes. Connect each Microsoft identity to Carly, add Carly to Claude once as a custom connector, and one conversation can search or act in whichever mailbox you name.
What one conversation can do afterwards
- Search mailboxes from two employers in a single question.
- Summarize what needs attention, grouped by account.
- Compare a contract thread in one tenant against another.
- Draft or send from the exact address you choose.
- Move, flag, or categorize in the correct mailbox.
- Check several calendars for conflicts before proposing a time.
The mailboxes stay separate. Carly handles account routing while Claude does the reading, comparison, and drafting.
What Claude’s Microsoft 365 connector does natively
Anthropic’s Microsoft 365 connector reaches Outlook mail, calendar, OneDrive, and SharePoint for the account you authorize.
Claude's Microsoft 365 connector gained write tools in July 2026 — it can draft and send mail, manage calendar events, and create or update files in OneDrive and SharePoint. They are off by default, reject anything with an attachment, and need you in the conversation: a scheduled task can read your mail, but it will not send on your behalf while you are away.
That is a genuinely capable connection, and it is worth knowing it goes further on Microsoft than on Google: Claude’s Gmail connector stops at a draft you send yourself, while Microsoft 365 can actually send. What it does not do is hold two Microsoft identities at once.
Ruling out the cases you do not need Carly for
| What you have | Best setup |
|---|---|
| A second Microsoft 365 login at another company | Connect it separately through Carly |
| A personal Outlook.com address plus a work account | Connect each one through Carly |
| A shared mailbox in a tenant you already reach | Try the native connector first |
| A delegated mailbox or folder | Try your primary identity’s existing access first |
Shared and delegated mailboxes ride along with the identity that already has rights to them. Independent logins at separate companies are the gap.
Two limits to plan around
Claude’s M365 write tools are off by default and need an administrator to enable them. They also reject anything with an attachment, and they need you in the conversation: a scheduled Cowork task can read your mail, but it will not send on your behalf while you are away. If the point is unattended mailbox work, that is the constraint to design around rather than the account count.
1. Give each Microsoft account a role
For example, all fictional:
| Address | Role |
|---|---|
fictional.priya.raman@outlook.com | Personal |
fictional.priya.raman@unilever.com | Main Company |
fictional.priya.raman@bosch.com | Client |
Use the role when searching and the full address before any send or modification.
2. Connect every Outlook account to Carly
- Sign in at carlyassistant.com.
- Open carlyassistant.com/integrations.
- Find Outlook and click Connect.
- Sign in to the first Microsoft identity and approve access.
- Confirm the connected address in Carly.
Repeat for every additional tenant. Use a private window if Microsoft preselects the previous login, and verify the full address after each authorization.
Each tenant approves independently. One company’s administrator declining does not block the others.
3. Add Carly to Claude
- Open Settings.
- Go to Connectors.
- Choose Add custom connector.
- Paste
https://carlyassistant.com/mcp/. - Complete authorization and sign in to the Carly workspace holding the mailboxes.
Claude will list the tools the connector exposes. Keep the mail and calendar tools enabled and switch off anything you do not want in play while testing.
4. Test every address read-only first
One mailbox per prompt:
In
fictional.priya.raman@unilever.com, list the sender and subject of the five newest unread messages. Do not change anything.
In
fictional.priya.raman@bosch.com, find the newest thread containing “statement of work.” State the source account and do not draft.
Then a cross-account search:
Search the Unilever and Bosch example accounts for “invoice” from the last 30 days. Include the full source address in every row.
Once Claude reliably attributes each result, move on to drafts, categories, sends, and calendar work.
5. Reuse this routing prompt
Treat
fictional.priya.raman@outlook.comas Personal,fictional.priya.raman@unilever.comas Main Company, andfictional.priya.raman@bosch.comas Client. Always state the target address before changing data. Ask before sends, moves, deletes, categories, or calendar changes.
Then name the target in each action:
Draft the reply from
fictional.priya.raman@unilever.com. Do not send yet.
Move this thread to Archive in
fictional.priya.raman@bosch.comonly.
Send the approved reply from the mailbox that received the original message.
Native Microsoft 365 connector versus Carly in Claude
| Need | Native M365 connector | Carly connector |
|---|---|---|
| Search one Microsoft identity | Yes | Yes |
| Hold several independent logins at once | No | Yes |
| Compare mailboxes from two tenants | No | Yes |
| Send mail | Yes, once an admin enables write tools | Yes |
| Handle messages with attachments | Refused | Yes |
| Act during an unattended scheduled run | Read-only | Yes |
| Run the same routing outside Claude | No | Yes |
Carly makes several Outlook connections addressable from one conversation, and the routing keeps working after you close it. Carly offers free Zapier-style workflows; AI agents start at $35/month.
Quick fixes when a mailbox does not appear
| Problem | Fix |
|---|---|
| Microsoft connected the same mailbox twice | Remove the duplicate and reconnect from a private window |
| A tenant blocks authorization | Ask that tenant’s Microsoft 365 administrator to approve Carly |
| Custom connector option is missing | Check that your Claude plan allows custom connectors |
| A send is refused | Check for an attachment, and confirm write tools are enabled |
| Claude queries the wrong mailbox | Use the full address and require source attribution |
Frequently asked questions
Can Claude natively connect two Outlook accounts?
The Microsoft 365 connector authorizes one Microsoft identity. Carly is the direct way to make several separately authorized mailboxes available in one conversation.
Can I mix a personal Outlook.com address with work accounts?
Yes. Connect each Microsoft identity to Carly separately and label every address with a clear Personal or Work role.
Will a scheduled Claude task send from the right mailbox?
Claude’s own M365 write tools need you in the conversation, so unattended runs stay read-only there. Route the send through Carly if it has to happen while you are away.
Related: Claude + Outlook · Multiple Outlook accounts in Claude Cowork · Multiple Gmail accounts in Claude · Manage multiple email accounts with AI · Carly’s Outlook integration
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