My email is on the bounceback list and I on't understand why

I keep getting notifications that my email is on the bounceback list and don't understand why. The email is steve.preston@phila.gov

I have checked and the email address in our bounce list.

steve.preston@phila.gov is IN  the bounce list

Reason(s) : smtp; 550 5.7.606 Access denied, banned sending IP

However, I have removed the email address from our bounce list.

Please follow these links to know how you can avoid any further email bouncing and get rid off it if this occurs again.

https://www.jotform.com/help/208-How-to-Prevent-Email-Bouncing-Related-Issues

https://www.jotform.com/help/262-How-to-Remove-Your-Email-Address-from-Bounce-List

Let us know if you have any further query.