User Unable to Send Emails – Attachment Error in Outlook New

Question

User Unable to Send Emails – Attachment Error in Outlook New

Maksymilian Zaczek 40

Hello,

Our user has reported an issue where, every time he tries to send an email from the shared inbox (which is our internal from Microsoft Exchange), he receives an error message.

Unfortunately, the screenshot is in Polish, but the translated message reads:

"An error occurred while sending the email because at least one attachment could not be sent. Please try again."

What makes this issue unusual is that it occurs every time the user attempts to send an email from this mailbox, regardless of whether any attachments are included. We have already tried reinstalling the new Outlook client, but the problem persists.

Could someone please provide actionable troubleshooting steps or guidance on how to further investigate and resolve this issue?

Thank you in advance for your assistance.

Kind regards,

Maksymilian Zaczek

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Answer 1

Anonymous

Hi Maksymilian Zaczek

I have tried to replicate the same behavior in my test environment, and I was able to send emails successfully both with and without attachments.

To help me better understand the situation and provide more accurate insights, could you please help confirm the following:

Does the issue also occur when using Outlook on the web?
Is the affected user able to send emails normally when using their own mailbox?
Can other users who have Send As permission for the shared mailbox send emails with attachments successfully?

If I’ve misunderstood any part of your situation, or if you have further questions or updates, please don’t hesitate to reply.

Thank you for your time, and I look forward to hearing from you soon.

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Maksymilian Zaczek 40 Reputation points

2026-07-07T10:24:43.3933333+00:00
Hi @Anonymous

Thank you for your response.

Here are my answer:

The issue does not occur in Outlook on the web.

The user is able to send emails from their own mailbox without any issues. They can also send emails from the shared mailbox, but it often requires multiple attempts and a lot of clicking before the message is actually sent.

Other users with access to the same shared mailbox are able to send emails normally.

Based on these observations, I suspect the issue may be related to a corrupted cache within the New Outlook application on this specific workstation.

Is there a way to clear or rebuild the cache for New Outlook for this user? Alternatively, are there any recommended troubleshooting steps.

I have already Terminate, Reset, Repair on Outlook new

Kind regards,

Maksymilian Zaczek
Anonymous

2026-07-07T11:41:08.2266667+00:00

Hi Maksymilian Zaczek
Before proceeding with another reinstallation of the new Outlook, I would like to suggest trying a reset of New Outlook for Windows first.

To do this, press Windows + R, enter the following command: olk.exe -reset

Please allow the command to finish running before opening Outlook again.

Once you have completed this step, please let me know how it goes.
Anonymous

2026-07-08T13:42:02.9+00:00

Hi Maksymilian Zaczek
Hope you're having a good day.

May I ask if there have been any updates since our last exchange?

I’d appreciate any updates you can provide.
Maksymilian Zaczek 40 Reputation points

2026-07-09T11:15:02.49+00:00

Hi Vergil-V,

Everything works after using command olk.exe -reset.

Thank you.
Anonymous

2026-07-09T12:41:41.07+00:00

Hi Maksymilian Zaczek
Thank you for your confirmation.

I am happy to hear that my support was helpful.