My website sends emails to users via SendGrid, a transactional email delivery platform. SendGrid accounts have a reputation bar. When your emails bounce or get marked as spam, your reputation goes down. If your reputation goes below 70%, your account is subject to review.
There's a box on my site in which people can provide their email addresses. What if a troll enters nonexistent email addresses or email addresses that belong to other people? My site is new and unpopular (less than 10 views a day), so this behavior is sure to negatively affect my SendGrid reputation.
How do I manage these troublesome users?