Hi Rans,
1. Yes, the generated code is just an embedded JavaScript code, and due to HTML tag is supported in PHP, thus we can use the script in PHP page.
2. Yes, after user submitted data, a XMLHttpRequest will be sent to Dynamics 365 back-end server to create new record or update existing match record.
3. Could you share me more details about your current situation?
As per my understanding, we just need to make sure the domain is owned by us regardless of external users' email addresses.
e.g: I have a website whose domain is www.clofly.com, what I should do is to authenticate/configure it in both Dynamics 365 setting and domain provider DNS setting page.
Then any external users with different email addresses(outlook or gmail) can submit their data then get pre-filled form if "remember me" option was checked.
Regards,
Clofly
