Duplicate Attachments

Question

Duplicate Attachments

James, Kelsea 20

Hi,

I have a reoccurring issue where the new outlook frequently doubles an attachment. Example, if I attach a file called YTD Report 2026, the sent and received email will show a second attachment with the same name and content. There are no issues opening both files.

For additional context, any removed attachments also stay attached once sent. Example, if I incorrectly attach a file called YTD Report July 2026, and remove that file to instead attached YTD Report August 2026, after the email is sent, both files for July and August appear, despite ensuring that the July file was removed.

I have attempted to prevent the above by restarting the email entirely, clearing all relative drafts if applicable and reducing attachments to once.

What causes this and how do I prevent it?

Ruby Nguyen 400 Reputation points

2026-08-05T23:23:59.2233333+00:00

Dear James,

I hope you're having a good week.

I'm just checking in to see if there have been any updates on the issue. I hope things are moving in the right direction and that a resolution is near.

Whenever you have an update, I'd be grateful if you could let me know.

Thanks again for your help and time.

Answer accepted by question author

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Your answer

Ruby Nguyen 400 Reputation points

2026-08-05T23:23:59.2233333+00:00

Dear James,

I hope you're having a good week.

I'm just checking in to see if there have been any updates on the issue. I hope things are moving in the right direction and that a resolution is near.

Whenever you have an update, I'd be grateful if you could let me know.

Thanks again for your help and time.

Answer 1

Good day James, and I appreciate the clear explanation of your concern.

Based on your description, this may be related to how Outlook saves or syncs the draft before sending. This can be caused by cache issues, add-ins, an outdated Outlook version or a corrupted profile.

Since you didn't mentioned using New Outlook desktop app or Outlook on the web, here are some options you can try:

Ensure that your operating system, web browser and New Outlook app are fully updated.

Option 1: Test from Outlook on the web

Please test the same attachment workflow from Outlook on the web.

If the issue doesn't happen in Outlook on the web, this points to the New Outlook for desktop app cache, local state, or client-side sync behavior rather than the mailbox itself.

Option 2: Clear the New Outlook local cache

Close the Outlook app completely.

Open the Run dialog by pressing Windows + R.

Type or paste the following command and click OK:

olk.exe --devtools

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The new Outlook will open (you may need to sign in), and the DevTools window will appear.

In DevTools:

Click Application on the toolbar.

Clear local storage cache: Under Storage, find https://outlook.office.com under Local Storage, right-click it, and select Clear.

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Clear cookies: Under Cookies, locate https://outlook.office.com, right-click it, and select Clear.

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Close the DevTools window.

Once completed, the cache for the New Outlook will be cleared. Please note that this process removes temporary files, including saved login credentials, so you may need to sign in again.

Option 3: Check New Outlook add-ins

Some add-ins that interact with attachments can inadvertently affect how files are added, removed, or synchronized.

Open New Outlook > Go to More apps > Select Add apps > Manage your apps.

Remove or disable one add-in at a time.

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Restart new Outlook.

Send a new test email with attachments.

Option 4: Repair New Outlook app

Open Windows Settings > Go to Apps > Installed Apps > Locate Outlook app.

Select Advanced Options > Scroll down and choose Repair.

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Once the repair is complete, reopen Outlook and test again.

Option 5: Contact your organization's IT admin

If the issue still persists after trying the steps above, I recommend reaching out to your IT administrator to create a support ticket via Microsoft 365 Admin Center > Support > Help & Support for further backend investigation. In case you do not know who is your IT admin, kindly refer to this article: How do I find my Microsoft 365 admin? - Microsoft Support

A technical support engineer can perform a remote session to investigate the situation, verify the backend configurations, and run any necessary synchronization tools to resolve the problem. If the issue requires further attention, they can escalate it to a specialized team for deeper analysis.

I hope this information is helpful. If you have any questions or need further support, please don’t hesitate to reach out at any time.

Thank you for your patience and understanding.

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