This error most often indicates that you have reached our limit for sending mail for the given hour. Mails are limited to 1500 per hour per user. On the other hand, please be sure that mass mailing (spamming) is not allowed and you may risk your account being suspended.
This limit has been applied to curb any spam attacks that might take place on our servers. We don’t have this limit in place to inconvenience you, but rather to protect us all from the very pervasive problem of spam.
