Hey! First, I would use Jotform. It’s so easy to modify and alter forms. Then you have to make sure that all Jotform domains are whitelisted within Outlook. You can see the list here: https://www.jotform.com/help/145-Whitelisting-JotForm-IP-Addresses-and-Domains I just had a client have this exact problem.

Even if you don’t go with Jotform this should give you some good insight!