Email Security providers such as Microsoft Defender and Proofpoint allow the enablememt of Safe Links in Microsoft 365 which are URL rewrites used for security purposes. This article will provide information on potential issues this can cause with Webex as well as a solution.
Safe Links policies are part of Microsoft Advanced Threat Protection (ATP) and Exchange Online Protection (EOP) services. These policies can be configured to rewrite URLs which can cause issues when joining a Webex meeting from the App or a device. If this is enabled, meeting join URLs will be rewritten to the safelinks.protection.outlook.com domain.
SOLUTION
In your email security policy for safe links, make a new entry to exclude *.webex.com from URL rewrites.
Please reference this guide to learn more about the "Do not rewrite the following URLs" option in Microsoft Defender
