Power Platform Community Forum Thread Details

Goal:

I want to create a Power Automate flow that:

Triggers when a new email arrives in a shared mailbox (including attachments).
Loops through each attachment and checks if the file extension is .xlsx.
Sends the file in a POST request to an API that works correctly when tested in Postman.

Problem:

Even though my email trigger has "Include Attachments" enabled, I cannot correctly send the file content in the HTTP POST request. My API either rejects the file or does not receive it in the correct format.

Current Setup:

Trigger: "When a new email arrives (V3)"
- ✅ Include Attachments: Yes
Apply to each (Attachments)
- Condition: Attachments Name ends with .xlsx
- HTTP POST Request (multipart/form-data):
```
 
```
  json
  
  { "$content-type": "multipart/form-data; boundary=--------------------------208446390803225736562660", "$multipart": [ { "headers": { "Content-Disposition": "form-data; name=\"file\"; filename=\"@{items('Apply_to_each')?['Name']}\"", "Content-Type": "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet" }, "body": { "$content-type": "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet", "$content": "@{base64(items('Apply_to_each')?['ContentBytes'])}" } } ] }

What I've Tried:

✅ Confirmed my API works in Postman (it correctly processes .xlsx files).
✅ Copied the request body sent through the postman call (except for dynamic content of course)
✅ Checked that attachments are included in the trigger.
❌ No matter how I format the request, the API either does not receive the file correctly and returns nothing to process as it could not read it.

Question:

How should I correctly format the HTTP request body in Power Automate to send the .xlsx file as a valid multipart/form-data attachment?
More specifically, what should be the value of $content ?
Do I need to manually convert the file to base64 or send it as raw binary?

Thanks in advance for any help!

Categories:

Building flows