Microsoft Outlook APIConnect Microsoft Outlook without building on its API
Microsoft Outlook has a REST API through Microsoft Graph. Self-serve for any developer who registers an Entra app, but mailbox access requires a Microsoft 365/Exchange Online or Outlook.com account and consent. If you're reading the docs because you need Microsoft Outlook to talk to the rest of your stack, Caddi does that without you writing or maintaining integration code: you show it the job once, and it runs it across Microsoft Outlook and your other tools.
- APIREST (JSON)
- AuthOAuth 2.0
- AccessSelf-serve
What the Microsoft Outlook API gives you
- Type
- REST (JSON)
- Authentication
- OAuth 2.0 via Microsoft Entra ID (delegated or app-only)
- Who can get access
- Self-serve for any developer who registers an Entra app, but mailbox access requires a Microsoft 365/Exchange Online or Outlook.com account and consent.
- What it covers
- Messages, mail folders, rules, attachments, events, calendars, and categories.
- Limits
- 10,000 requests per 10 minutes, 4 concurrent requests, and 150 MB upload per 5 minutes per app per mailbox.
Official docs: learn.microsoft.com. Checked September 2026. Vendors change access terms, so confirm with Microsoft Outlook before you build.
Building on the Microsoft Outlook API vs. having Caddi run it
| The job | Build it on the API | With Caddi |
|---|---|---|
| Getting access | Register an app, get Microsoft Outlook credentials, and manage tokens and refreshes. | Connect your Microsoft Outlook account once. Caddi holds the connection. |
| Writing the integration | A developer maps fields, handles pagination, retries and rate limits, and writes the sync. | You show Caddi the Microsoft Outlook task the way you'd train a new hire. It writes verified code for it. |
| Steps the API doesn't cover | Screens with no endpoint stay manual, or need a separate RPA tool. | Caddi uses a secure, audited browser session where there's no API, in the same automation. |
| The other systems in the loop | Each extra tool is another API, another set of credentials, another integration to own. | One automation runs across all the tools the job touches. |
| Keeping it running | Someone owns the code when the API version, fields or your process change. | Every automation is reviewed before it runs in production, and every run is logged. |
Building on the API is the right call when you have engineers and the integration is your product. When the goal is getting Microsoft Outlook work off someone's desk, the build is the slow part.
What teams usually want the Microsoft Outlook API for
Claim Email Thread Triage
Caddi reviews the oldest claim email threads, identifies what follow-up is needed, and sends the next email — reducing manual thread triage for legal operations teams.
New Matter Setup
Caddi extracts client and matter details from new matter request emails, creates the client and matter workspace when needed, and files intake documents with the right attributes.
Cash Receipt Reconciliation
Caddi extracts invoice and payment details from cash receipt emails and writes them to the correct tracker row, reducing manual reconciliation work for billing and finance teams.
Meeting Invitation Emails
Caddi pulls verified client contact details to draft and send meeting invitation emails from a saved template and creates a follow-up task.
Microsoft Outlook API questions
Does Microsoft Outlook have an API?
Yes. Microsoft Outlook has a REST API through Microsoft Graph, authenticated with OAuth 2.0 via Microsoft Entra ID (delegated or app-only). The official documentation is at https://learn.microsoft.com/en-us/graph/outlook-mail-concept-overview.
How do I get access to the Microsoft Outlook API?
Self-serve for any developer who registers an Entra app, but mailbox access requires a Microsoft 365/Exchange Online or Outlook.com account and consent.
Does the Microsoft Outlook API have rate limits?
10,000 requests per 10 minutes, 4 concurrent requests, and 150 MB upload per 5 minutes per app per mailbox.
Can I connect Microsoft Outlook to my other tools without writing code against its API?
Yes. With Caddi you show the Microsoft Outlook task once, the way you'd train a new hire, and Caddi builds it as verified code that runs across Microsoft Outlook and the other tools the job touches. Where a step has no API, Caddi uses a secure, audited browser session in the same automation.
Do I need a developer to automate Microsoft Outlook with Caddi?
No. There is no integration code for you to write or maintain. Every automation Caddi builds for Microsoft Outlook is reviewed before it runs in production, and every run is logged.
Connect Microsoft Outlook without the build.
Drop your work email and pick a time. We'll show you Caddi running your Microsoft Outlook workflow end to end.