today we wanted to send a press announcement via email to about few hundreds (at least 300) recipients at blind copy.

Unfortunately we received from the mail server following error message 'Unable to send message;Reason:550 5.4.6 Mail rate exceeded limit'. So we reduced the amount of recipients consistently until we reached the number of 3 recipients, we were surprised that even at this low number your server remained to return the error message.

May you can help us regarding this problem?

best regards, Reza Anwar