If you receive an email error: Administrative prohibition or 550 Administrative prohibition:
This means that you cannot send email to that server right now. You can email email@example.com to find out how long it will be before we enable sending to that server again. This usually means that either we have a security issue or one of our clients are attacking someone at that server so we have administratively blocked all traffic there.
If someone is sending you an email and they receive an Administrative prohibition error or 550 Administrative prohibition:
This means that they, the sending ISP is broken or probably maybe has a security issue and that they, the sending email service have administratively blocked sending to Nkosi as they may be attacking us or for some other reason has decided to block us. The Sender has to contact their ISP and ask when they will be able to lift the administrative prohibition or find out why they cannot send email.