This seems inefficient, and it is, but there's a subset of people with whom I communicate in my industry, and they almost always will only answer one of my questions if I put multiple questions in an email. Even a simple one like:
> Two quick questions for you:
> 1. Do you want this or that?
> 2. Which do you like better, A or B?
Limiting to a single question and then following up with a second question takes longer, but I don't feel rude having to point out the second question that was missed/ignored from my initial email.