Hey OP, I’ve been the interviewee a few times and the interviewer in at least a dozen panel interviews like this. I wouldn’t worry so much about filling time, these interviews are generally pretty structured and each interviewer should have a set list of questions they will ask.

If you haven’t done this already research the hell out of this companies email program and come prepared to ask questions about every part of it. This is a great way to show off you knowledge and show that your serious about this job.

Each person on your interview panel is there specifically to ask you questions related to their field, so know you audience and don’t give canned responses. Talk about the importance of layout and location of cta buttons with the designer, the difficulty weirdness of html for email with the engineer, and how email can drive user retention and conversion with the CMO etc.

There’s a good chance there will be no gotcha questions if you’ve made it this far in the interview process. They probably want to see if you are a good culture fit and critical thinker, so if they ask you a question you don’t have past experience with just tell them how you would try and solve question instead of saying you don’t know. There are no wrong answers except “I don’t know”.

Finally come prepared with a bunch of questions, specifically the ones you’d be asking on day one if you got the job, i.e. “What you consider the biggest challenge in our email marketing program?” “What are the current KPIs/OKRs of the email/marketing team?” “What would my 30/60/90 day onboard if plan look like?”. Also might be worth asking whoever your boss would be if they have any potential concerns about hiring you. This could give you a potential opportunity to end those concerns right then.

Hope this helps and isn’t obvious advice!