Unable to send message: Reason 550 5.4.6 mail rate exceeded limit

Unable to send message: Reason 550 5.4.6 mail rate exceeded limit

Hi there,

I was in the process of sending information to key members when I was blocked from sending emails. Could you please unblock president@uoacheernz.org?

Secondly if an account is blocked, how long will it take to automatically unblock?