Why "outlook blocked access to the following potentially unsafe attachments" message appears only on desktop app

Question

*Environment: Windows10, office365

I am seeking for some explanation.

As the title goes the attachment does not appear with the message only when the email is open on desktop app. The attachment we have the issue for is .zip file and .zi (name changed intentionally) file.

Both of the files can be accessed OWA or simply saving the email on the PC locally makes them appear. But I want to know why this happens only on the desktop app.

Change PC -> same result
create new profile -> same result

Answer 1

Thank you again for your advice. Due to our situation, it is not very feasible to test things mentioned by you in our environment, but appreciate your input. Thank you!

Answer 2

Hello yk_672,

Thank for your reply!

This is security protection added in Outlook for Windows and will not affected in Outlook on the web. Thus it will happen on Outlook client side. Since you are facing the issue on the attachments with .zip and .zi files in Outlook for Windows, you may perform further steps to narrow down this issue. For my suggestion, you may try following workaround as shared:

1. Firstly, you may check if this case only exists on one specific attachment with .zip file or all of them. Please also try to compress the attached file as .zip format using different software such as WinZip, 7-zip etc and check if there is any difference.
2. Outlook works best when it's up to date. We recommend setting Windows Update to automatically download and install recommended updates. Bug fixes, new features, and performance enhancements are released regularly. To install the latest Windows and Office updates, see Install Office updates.
3. For further investigation, you may also test on different PCs with different Outlook version to check if there is any difference.

Update history for Microsoft 365 Apps (listed by date) - Office release notes | Microsoft Learn

If above workaround tried but no result, it is recommended that you may contact Microsoft Technical Support Teamwith a ticket opened: Ways to contact support for business products - Admin help. Go to Office365 admin center>Support>New Service Request. The support team over there has higher permission than us, they can remotely help you and collect logs at your convenience. They can also involve more resources to investigate the issue from backend side. This would be the most efficient way in handling this case for you. (Please Note: If you are not sure who is admin, you may check this Microsoft article: How do I find my Microsoft 365 admin? - Microsoft Support)

Again, your understanding and patience will be appreciated.

Thank you!

Microsoft Community Moderator

Answer 3

Thank you for your response, Eleni,
Can you follow up please?

1.
So OWA should NOT be affected by blocking? Is having the dissapearnce only on the desktop app expected?

2.
For my suggestion, you may further check above shared article and they also provide some scenarios about how to open a blocked attachment, and what types of attachments Outlook may block
-> Checked about types of files that are blocked. It is mentioned that a compressed file is not taken as a threat but as I mentinoed in the original post, the attachments having issue are .zip and .zi files.

Thank you in advance.

Answer 4

Hello yk_672,

Thank you for posting this case in Microsoft Community!

Based on your description: Why "Outlook blocked access to the following potentially unsafe attachments" message appears only on desktop app. I would like to cooperate with you working on this case. To clarify this case, all versions of Outlook client since Outlook 2000 Service Release 1 (SR1) include a security feature that blocks attachments posing a risk of viruses or other threats. Outlook blocks access to the attachment, but the attachment is present in the e-mail message. Thus in Outlook for Windows, when receiving an e-mail that contains an attachment, you may receive this alert message on top of the message or in the Reading Pane. See more information, you may check below article as reference:

Outlook blocked access to the following potentially unsafe attachments

Blocked attachments in Outlook

For my suggestion, you may further check above shared article and they also provide some scenarios about how to open a blocked attachment, and what types of attachments Outlook may block. We also recommend using OneDrive and sending the recipient a link to the file instead.

Hope the above workaround would be helpful. If you need further assistance, please feel free to let me know, I will keep assisting you.

Your understanding and patience will be appreciated.

Thank you!

Microsoft Community Moderator