Outlook Add-ins
The Developer's Guide to Overcoming Outlook API Restrictions
NX
7 min read
2026-05-07
Bypassing sandbox restrictions securely
Bridging the Gap with Graph API
When Office.js cannot read a specific MAPI property or header, your add-in can call a secure backend that uses the Graph API to fetch the full message metadata in JSON format.
Expert Insight
For large attachments (>25MB), use the Graph API's 'Upload Session' feature rather than trying to process the binary data within the browser-based Task Pane.
Using Upload Sessions for stability
Handling Large Attachments
The standard Office.js attachment API has size limits. For enterprise file transfers, an asynchronous backend upload is mandatory.
javascript
const uploadSession = await client.api('/me/messages/{id}/attachments/createUploadSession').post();
// Then upload the file in chunks...Summary
Every restriction in Office.js has a workaround if you leverage the full power of Microsoft Graph.
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NexaAI Solutions
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