Too Many Failures?

Hi, Have a client who is struggling connecting to the server for emails. It seems theres a bunch of failed login attempts - Currently remotely connected to one of their machines now and some of the settings are incorrect. Fixed all the settings but now getting the following error message in the email client: LOGIN DENIED TOO MANY FAILURES Their public IP is already listed in the allowed list in CSF Firewall and also the chbrute force protection. Is there anything else I should be looking at to get it reset so they can log in? Cheers,