Can't open the excel sheets my flow sends to my Onedrive folder

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Posted on by j1700

The goal of my flow is to send the excel sheet content of an automatic email sent to my shared mailbox every Friday into my personal onedrive folder called Source Data as seen above. The File name (fx) is: concat(formatDateTime(utcNow(), 'yyyy-MM-dd'), '_', items('Apply_to_each')?['name'])

The File Content is: Attachments Content

The flow seems to detect the email fine and automatically sends an excel sheet to my Onedrive folder, however when i try to open it - it says:

Is there any way to fix this? Thanks

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Valantis 2,535 on at

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Hi @j1700,

The issue is that the Create file action saves the attachment using Attachments Content directly, but Power Automate passes this as base64 encoded binary. OneDrive saves it correctly but Excel cannot open it because the file content does not match the extension.

The fix is to wrap the file content with the base64ToBinary() function instead of using Attachments Content directly.
In the File Content field of your Create file action, replace Attachments Content with this expression:

base64ToBinary(items('Apply_to_each')?['contentBytes'])

This converts the attachment from base64 to proper binary before saving, which is what OneDrive needs to store the file in a format Excel can open correctly.

Best regards,

Valantis

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📝 https://valantisond365.com/

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Ellis Karim 11,994 Super User 2026 Season 1 on at

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@j1700,

See also: How to Save Files to SharePoint Without Corruption Using Power Automate – Ellis Karim's Blog which shows the following method:

Ellis Karim
elliskarim.com | LinkedIn | Bluesky
If this solved your issue, please mark it as ✅ Accepted Answer. If it helped, feel free to give it a 🩷 Like!

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chiaraalina 1,864 Super User 2026 Season 1 on at

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Hi

In my opinion, this should work without any extra steps.

Microsoft docs say that with “Include Attachments = Yes”, the trigger already provides the attachment content, so using “Attachments Content” directly is supported.

https://learn.microsoft.com/en-us/troubleshoot/power-platform/power-automate/flow-run-issues/issues-triggering-emails-with-attachments-from-shared-mailbox

Maybe check:

Open the original attachment from the email -> does it work?
Check file size -> is it very large?
Check you’re not picking the wrong attachment
Test with another file first

Check if the email/attachment is encrypted

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