Calendar Problems

How to Fix Outlook Calendar Invitations Appearing as HTML Code

Bushra Parveen Oct 10, 2026 868 views

Question details

The user needs to troubleshoot and resolve an issue where Outlook calendar invitations display as raw HTML code or malformed events instead of standard meeting requests.

How to Fix Outlook Calendar Invitations Appearing as HTML Code

Product: Microsoft Outlook
Device & OS: not provided
Scenario: Receiving or sending calendar invitations, particularly involving Microsoft Teams meetings.
Observed behavior: Calendar invitations arrive displaying raw HTML code, generate duplicate messages, or appear as malformed Teams meeting events.

Before you start

Before troubleshooting, check if the issue is isolated to a single user or affects multiple people, and verify if the problematic invitations are exclusively Microsoft Teams meetings.

Solution 1Recommended

Verify and Enable the Teams Meeting Add-in

A disabled or malfunctioning Teams Meeting add-in is a common cause of malformed meeting invitations.

Because these are often Teams meetings, a disabled or corrupted add-in can disrupt the formatting process when the invitation is generated or received.

Open Outlook Options

Launch Microsoft Outlook, click on the 'File' tab in the top-left corner, and select 'Options' from the bottom of the menu.

Access Add-ins

In the Outlook Options window, click on 'Add-ins' located in the left sidebar.

Enable the Teams Add-in

At the bottom of the window, ensure 'COM Add-ins' is selected in the 'Manage' drop-down and click 'Go'. Check the box next to 'Microsoft Teams Meeting Add-in for Microsoft Office' and click 'OK'.

Verify and Enable the Teams Meeting Add-in

Solution 2

Switch to Plain Text or HTML Formatting

Rich Text Format (RTF) can cause compatibility issues and result in invitations displaying as raw code.

Solution 3

Review Antivirus and Security Scanning

Overly aggressive email scanning by security software can strip formatting or cause duplicate messages.

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Frequently Asked Questions

Why are my Outlook meeting invites showing up as source code?

This usually happens when the Teams Meeting add-in crashes or is disabled, or when an aggressive antivirus scanner intercepts and modifies the incoming email formatting before it reaches your inbox.

Does using Rich Text Format (RTF) cause calendar invite issues?

Yes, sending invitations in RTF can cause compatibility problems with recipients using different email clients, often resulting in the invitation appearing as raw HTML code or unreadable attachments like winmail.dat. Always use HTML or Plain Text for best compatibility.

What should I do if the issue persists after troubleshooting add-ins and formats?

If local troubleshooting does not work, try logging into Outlook on the Web (OWA) to see if the invites display correctly there. If they do, collect the message headers of the corrupted email and provide them to your organization's IT administrator for deeper investigation.

Outlook & Email Problems