Outlook classic for Windows just started showing incoming emails only in plain text

Edward Fitchett 45 Reputation points
2025-08-12T01:08:38.1733333+00:00

MS 365 (Outlook) just started showing incoming emails only in plain text with the heading "X-RG-Rigid:" with a long number afterward such as "687D27190201933" which is different for each email - I have checked the Trust Center - I have run an MS 365 basic repair - I have run Outlook in safe mode - same thing.....

Outlook | Windows | Classic Outlook for Windows | For home

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Answer accepted by question author
Jason Nicholson 100 Reputation points
2025-08-13T03:04:16.6733333+00:00

Thank you for your patience.

Could you please confirm if you have Bitdefender antivirus/antispam software installed in your PC?

If yes, could you please follow the below steps and check the behavior.

  • Please open Bitdefender
  • Click on Protection > Online Threat Prevention
  • Disable 'Encrypted Web Scanning'

Outlook support suggested this, I have Bitdefender and this fixed the issue!

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  1. THOMAS MECCO 0 Reputation points
    2026-07-17T17:24:04.9666667+00:00

    I had all my setting correct ( trust center) And display as (HTML)

    This issue was "Immersive Reader" was enabled

    You need to turn it off in 2 places

    A) In an already received email. You will see it in the email tool bar at the top of the mail ( disable it)

    B) Open a new email to send and also disable it.

    Those 2 actions will correct the issue.

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  2. LorMard 20 Reputation points
    2025-08-14T13:19:42.0266667+00:00

    Thanks to everyone who contributed. I’ve just received a resolution from Bitdefender stating that the issue has been fixed. It updates automatically every hour, so it should work fine. I’ve checked on one of my PCs, and it works perfectly. I truly appreciate your help.

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    2 people found this answer helpful.
  3. Stefan Blom 352.4K Reputation points MVP Volunteer Moderator
    2025-08-12T09:06:13.1666667+00:00

    If this happens consistently with e-mail accounts that are NOT of the Microsoft Exchange or outlook.com types, the reason might be a bug with the classic Outlook for Windows. In Outlook, you can report it via Help > Feedback > Report a problem.

    Note that if you are using some third-party firewall or antivirus program, first check if it interferes with e-mail traffic in some way. Maybe you already tested this.

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  4. Adrian_A_ 8,900 Reputation points
    2025-08-12T01:56:55.39+00:00

    Thanks for the information you've shared. I’m here to help.

    Before we proceed, I'd like to confirm the following:

    1. Does the same email show up as plain text in your webmail, or only in Outlook?
    2. When did this start happening, and did anything change on your PC or email account around that time, like updates, new security software, or provider changes?
    3. Are all senders affected, or only certain ones?
    4. Which type of account is set up in Outlook? Is it POP3, IMAP, Exchange, or Microsoft 365?
    5. Are you using any third-party spam filters, antivirus email scanning, or firewalls that could modify incoming messages?

    In the meantime, while waiting for your answers, here's what you can do

    1. Check the same email in your webmail or Outlook Web App. If it looks the same there, the issue is at the server.
    2. Make sure “Read all standard mail in plain text” is unchecked in Outlook Trust Center settings.
    3. If you’re using POP3, switch to IMAP if possible.
    4. Contact your email provider and show them an example with full headers so they can fix the filtering.

    Kindly check the raw message headers in webmail or through a browser to see if the plain text is being sent from the server. If it is, the issue is at the provider’s side.

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