Yep. That is exactly what is supposed to happen. Hackers write programs that guess passwords all day long. If you try to guess at your password you look like one of those programs and you are therefore locked out by our firewall. You can wait a while and let the block clear on it's own or open a ticket and request it be manually cleared. IMPORTANT: if you want us to manually clear the firewall, be sure to tell us in your ticket what IP address you are trying (and failing) to connect from. There are literally thousands of IP addresses in the firewall at any one time and it is impossible for us to guess which one might be you. Visit this website from your affected device and tell us what IP it reports that you are coming from.
This can also happen to you if you are trying to log into email with the wrong username or password. Basically, any failed login attempt (of any sort) repeated often enough will cause the server to protect itself by refusing to connect with you.
NEVER try to guess your password. If you don't know it, use the password recovery tools.