Gmail rate contol érdekesség

Elég bizarr dologgal találkoztam a mail log-ban:

450-4.2.1 The Gmail user you are trying to contact is receiving
450-4.2.1 mail at a rate that prevents additional messages from
450-4.2.1 being delivered. Please resend your message at a later
450-4.2.1 time; if the user is able to receive mail at that time,
450 4.2.1 your message will be delivered. itt-jön-a-queue-id

A kérdés az, hogy mikortól számít "nagynak" a forgalom?