How to Connect Multiple Outlook Accounts to Gemini Spark
Gemini Spark has no Outlook connector — not one account, and not several. Its native reach is Google’s own apps. The route to Outlook is Spark’s custom MCP support, and that is also what solves the multi-mailbox problem in the same step.
Spark’s connected apps are Google-shaped
Google describes Spark as connecting “natively with your favorite Google apps like Gmail, Calendar, Drive, Docs, Sheets, Slides, YouTube, and Google Maps.” The June 2026 update widened that list to Google Tasks, Google Keep, Canva, Dropbox, Instacart, OpenTable, and Zillow Rentals.
Microsoft is absent from every version of that list. If your mail lives in Outlook, the native connector story ends here.
The custom MCP path is the whole answer
The same June update added support for “custom Model Context Protocol (MCP), giving you the ability to connect your favorite apps directly into Spark.” That is the supported way to give Spark a capability Google has not built, and it happens to make the account count irrelevant: Carly holds as many Microsoft identities as you authorize, and Spark talks to Carly once.
There is no such thing as an MCP trigger. The protocol's own working group states plainly that clients find out about server-side changes by polling for them, and a real event mechanism remains unshipped.
So an MCP connector answers when Spark asks. For mailbox work that has to happen while nobody is watching, put it in a Carly workflow rather than relying on the connection itself to notice anything.
Spark is also gated: Google says it is “currently available for Google AI Ultra subscribers over 18 in select countries as well as select business users.” Confirm your access on Google’s availability page before building on it.
What one Spark session can do afterwards
- Query Outlook mailboxes from two employers in one request.
- Summarize what needs attention, grouped by mailbox.
- Compare a 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 Outlook calendars alongside your Google ones.
That last one is the case worth the setup. A Google-first assistant that can also see the Microsoft calendars is exactly what Spark cannot do alone.
1. Give each Outlook account a role
For example, all fictional:
| Address | Role |
|---|---|
fictional.tomas.leroy@outlook.com | Personal |
fictional.tomas.leroy@arcelor.com | Main Company |
fictional.tomas.leroy@michelin.com | Client |
Use the role when querying and the full address before anything that changes a mailbox.
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 mailbox, using a private window if Microsoft preselects the previous login. Verify the full address after each authorization.
Carly connects personal Outlook.com addresses and Microsoft 365 work accounts alike, and each tenant approves independently, so one company’s administrator declining does not affect the others.
3. Add Carly to Spark over MCP
- Open Spark’s settings and find connected apps.
- Choose the option to add a custom MCP connector.
- Paste
https://carlyassistant.com/mcp/. - Complete authorization.
- Sign in to the Carly workspace holding the mailboxes.
Custom app support has rolled out unevenly across Spark’s platforms and tiers. If the option is missing, check your plan and platform against Google’s documentation before assuming the connector is the problem.
4. Test every address read-only first
One mailbox per prompt:
In
fictional.tomas.leroy@arcelor.com, list the sender and subject of the five newest unread messages. Do not change anything.
In
fictional.tomas.leroy@michelin.com, find the newest thread containing “tooling order.” State the source account and do not draft.
Then a cross-account query:
Search the ArcelorMittal and Michelin example accounts for “lead time” in the last 30 days. Include the full source address in every row.
Once Spark attributes every result to the right mailbox, move on to drafts, categories, sends, and calendar work.
5. Reuse this routing prompt
Treat
fictional.tomas.leroy@outlook.comas Personal,fictional.tomas.leroy@arcelor.comas Main Company, andfictional.tomas.leroy@michelin.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.tomas.leroy@arcelor.com. Do not send yet.
File this thread under Procurement in
fictional.tomas.leroy@michelin.comonly.
Send the approved reply from the mailbox that received the original message.
What Spark can reach, with and without Carly
| Need | Spark alone | Spark with Carly over MCP |
|---|---|---|
| Read Gmail for the signed-in account | Yes | Yes |
| Reach any Outlook mailbox | No | Yes |
| Hold several Microsoft identities | No | Yes |
| Compare Outlook and Gmail in one request | No | Yes |
| Send from a chosen Outlook address | No | Yes |
| See Outlook and Google calendars together | No | Yes |
| Keep the routing working outside Spark | No | Yes |
Carly is the supported bridge between a Google-first agent and a Microsoft mailbox, and it removes the account limit in the same move. Carly offers free Zapier-style workflows; AI agents start at $35/month.
Quick fixes when a mailbox does not appear
| Problem | Fix |
|---|---|
| No Outlook option in Spark’s app list | Expected; Spark has no native Microsoft connector |
| Custom MCP option is missing | Confirm your tier and platform against Google’s availability docs |
| A tenant blocks authorization | Ask that tenant’s Microsoft 365 administrator to approve Carly |
| Microsoft connected the same mailbox twice | Remove the duplicate and reconnect from a private window |
| Spark queries the wrong mailbox | Use the full address and require source attribution |
Frequently asked questions
Does Gemini Spark work with Outlook?
Not natively. Spark’s connected apps are Google’s own plus a short list of third-party partners, none of them Microsoft. Custom MCP is the supported route, and a Carly connector covers Outlook mail and calendar.
How many Outlook accounts can this reach?
As many as you authorize in Carly. Spark connects to Carly once, so adding a fourth mailbox does not change anything on the Spark side.
Can Spark send email through Outlook?
Not on its own. With Carly connected, sends run through the Outlook account you name, with that account’s permissions.
Related: What is Gemini Spark · Multiple Gmail accounts in Gemini Spark · Multiple Outlook accounts in Gemini · Manage multiple email accounts with AI · Carly’s Outlook integration
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