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PDF attachments got rejected and identified the attachment as spam.

Anonymous
2025-07-06T05:21:18+00:00

I have always been using my hotmail to send PDF as attachments, then beginning tonight 5 July 2025, all emails with PDF attachments got rejected and identified the attachment as spam. I'd read the Microsoft Q&A, and saw this had happened before. Can Microsoft solve this issue ASAP?? I need to send these attachments for business purposes

Outlook | Windows | Classic Outlook for Windows | For business

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  1. Anonymous
    2025-07-06T06:06:42+00:00

    Tried these 3 methods:

    1. the pdf I am trying to send are paystubs which will be unrecognizable when tried to open it in rich text format or plain text format
    2. paystubs are confidential information and not sure if I can share it on OneDrive
    3. zipping it may work, but it's annoying people have to download and unzip every time

    I am really hoping Microsoft can get this problem fixed

    Andre Lo

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  2. EmilyS726 225.5K Reputation points Independent Advisor
    2025-07-06T06:26:50+00:00

    Andre. Microsoft had to scale up the spam filter due to the increasing threats of an ongoing attack using pdf and html format email. This is not a problem but intentional. I don’t think it will be changed until the threats die down.

    Method 1 is the easiest to avoid being flagged by the spam filter. The plain text format is meant for the email body, not the pdf attachment itself. Please spend the time needed to read the instruction in the link I already shared with you and you would then realize how easy it is.

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  3. EmilyS726 225.5K Reputation points Independent Advisor
    2025-07-06T05:52:05+00:00

    Hello,

    Any chance you are trying to send an email with a PDF attachment?

    More and more email services providers have updated their spam filters due to rising zero-day phishing PDF campaigns. PDFs + HTML email are commonly used in phishing, so security systems scrutinize these more.

    You can consider these alternatives if you need to send PDF attachment -

    1. Probably quickest and easiest, if your email format is rich text/html, convert it to plain text. You might notice some of your email accounts could do it while some couldn't, or sending from different platforms (app vs. web) can yield different result too, because some are set to plain texts and some are not.

    Instruction can be found here: https://support.microsoft.com/office/change-the...

    1. Share it via a OneDrive link instead for the recipient to download.
    2. Zip it into a .zip file and attach it.
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