Hey @EBondil email clients don’t really have a wide support for custom code. Most typeforms will use scripts and connections that are not compatible with email clients, so HubSpot is rejecting this.
It looks like typeform has some small compatibility for direct email embeds which you can see here.
If this is the code you’re using and HubSpot is throwing this warning, you’ll likely need to create a custom email module to embed this.