New Question emails are not being send to all users

AOA Team!
Hope you are doing well. When anyone post a question on my website, I(admin) receive an email. But all the users on my website do not receive the mails. I have added their email addresses to the field below the admin section but all in vain. If I put one email address the I can receive email to that address. but not when I add more than one emails.
1st Question
I want to send New Question emails to all registered users. I have added their emails to section but it didn’t help. So how to send emails to all users?

2nd Question
The email which user receives are in spam. How to get the emails in inbox?
Thank you Team