Outlook desktop blocking wav attachment, only 1 user

M Tran 481 Reputation points

Apologies if I am posting in the wrong place. I am hoping someone can shed some lights or give me some suggestions.

I have one user, only one user, having this strange issue. She receives voicemail in her email with a wave attachment, but Outlook desktop app blocks this wave file (voice.wav). The attachment is not blocked in OWA. It is not blocked by our mimecast email filtered. It only gets blocked when it hits outlook desktop app.

What I did so far: used Level1Remove reg hack, completely re-installed office suite, logged her onto a totally different machine to see if it was her profile, put in a ticket with MS Support > the result was nothing worked!

I just don't know where else to look. No one has this problem in our organization. The affected user is on Windows 10 20H2. The strange thing here is, once in awhile outlook would let the wave attachment through, but most of the time, it blocks it with the message "outlook blocked access to the following potentially unsafe attachments".

If you have any suggestions for me to try, greatly appreciate it!

Thank you!

Outlook Management
Outlook Management
Outlook: A family of Microsoft email and calendar products.Management: The act or process of organizing, handling, directing or controlling something.
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  1. ChristyZhang-MSFT 21,671 Reputation points Microsoft Vendor

    Hi @MinaTran-2950 ,

    Welcome to our forum!

    According to your description, I have done research on the error "outlook blocked access to the following potentially unsafe attachments" you mentioned and found an official documentation on this: Outlook blocked access to the following potentially unsafe attachments, which introduces several methods to solve the problem of unable to open attachments.

    If you can contact the sender, it is recommended that you try to request the sender:

    1. Compress this attachment before sending.
    2. Change the suffix of this attachment before sending. After you receive the email, save the attachment and modify it yourself.

    If you can only operate after receiving this email, and if you have permission to change the outlook attachment security behavior, it's suggested that you could modify the registry and change Outlook's attachment security behavior. For specific steps and more information, please refer to the official documentation above.
    (It should be noted that if you modify the registry by mistake, serious problems may occur. Please back up the registry before operation.)

    Hope to help you!

    If the response is helpful, please click "Accept Answer" and upvote it.
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  2. Chris Wittry 1 Reputation point

    I don't have an answer, but I am also experiencing this same issue. I have several users, in several different organizations, all of them have the same brand of phone system (Fortivoice by Fortinet) and Outlook is blocking their WAV voicemail attachments with this same message. I have tried all of the recommended REGEDITs and none of them work. My users are all on 20H2 with all Office 365 updates installed. Hopefully this info helps find a common thread here.

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  3. M Tran 481 Reputation points

    I finally got the issue resolved. The fix was creating a mail flow rule in Exchange Online below.


    Anyone out there with similar issue, perhaps give this a try. Set the sender according to your VM system.

    Hope this helps.