In order to help combat spam, as well as to help prevent our servers and legitimate emails from being blocked by automated anti-spam filters the email rate limit is 300 message per 10 minutes. If this rate is exceeded, then our security system considers that to be “abusive” behavior and blocks your IP address from our network for 8 hours.
The calculation counts the number of recipients. So, 1 e-mail message with 300 addresses counts as 300 recipients. 30 e-mail messages with 10 addresses each also counts as 300 recipients. And 300 messages with 1 address each counts as 300 recipients.
The calculation is done every time an e-mail is received, and it looks back 10 minutes into the past from that point. So, for example, let’s say you sent e-mail to 200 recipients at 7:00 AM.
If you sent another e-mail at 7:02 AM, the system will look back to 6:52 AM and it will catch the 200 recipients at 7:00 AM, so if your 7:02 AM e-mail has more than 100 recipients, that would put you over the 300 limit.
If you sent an e-mail at 7:09 AM instead, it will look back to 6:59 AM, so it will still see the 200 recipients from 7:00 AM and anything over 100 recipients at 7:09 will again trigger the block.
If you were to send at 7:11 AM instead though, it would look back to 7:01 AM, and there would be 0 messages sent during that 10 minutes period, so you’d be able to send up to 300 messages at 7:11.
Additionally, this helps to ensure that no single customer’s mailing activities overwhelm our servers and create delays or other problems.
If you are emailing multiple addresses on a regular basis, please consider setting up an Email Forward to avoid exceeding the 300 message per 10 minutes limit. This allows you to send one e-mail to many addresses and will not have the same impact on your message ratio that mailing each address separately would.