You are reading this article probably, because you have tried to send an email via smtp server smtp.forpsi.com and such error was displayed
550 5.1.0 cNkj1y0022zrrQM01NkjaD policy violation, see https://support.forpsi.com/kb/a4081
More than 100 emails were sent from your public IP address in last hour, and more than half of these emails couldn't be delivered to target mailserver. So, they stayed awaiting in the queue of the smtp server smtp.forpsi.com.
Emails didn't have to be sent from your email account. Somebody, who uses the same public IP address as you, could send the emails.
To prevent overloading of smtp server smtp.forpsi.com, smtp access of your public IP address to the smtp server smtp.forpsi.com was temporarily blocked (access via POP3, IMAP and webmail still works).
The blocking of your public IP address will expire no later than in 60 minutes.
For more details, or if you need to unblock your account earlier, contact our customer support with an authorized ticket on https://support.forpsi.com/Main/frmTickets.aspx