You are reading this article probably, because you have tried to send an email via smtp server smtp.forpsi.com and such error has displayed
550 5.1.0 cNkj1y0022zrrQM01NkjaD policy violation, see https://support.forpsi.com/kb/a4079
More than 100 emails were sent from your public IP address in last hour, and more than half of these emails were addressed to invalid recipients (missed MX record, emails are rejected with the target mailserver ...)
This error means, that something with your emails is wrong. You may have invalid addresses of recipients or target mailservers reject your emails. In this case you get non delivery reports. It is neccessary to find out, why your emails are rejected. It is possible to read it in NDR messages.
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.
This is common scenario of spamming. From safety reasons, smtp access of your public IP to the smtp server smtp.forpsi.com was temporarily blocked (access via POP3, IMAP and webmail still works).
The blocking of your public IP will expire no later than in 60 minutes.
For more details, or if you need unblock your account earlier, contact our customer support with an authorized ticket on https://support.forpsi.com/Main/frmTickets.aspx