At the Before Arrival filtering point, blacklisted emails are rejected after the sender specifies the recipient address(es). Emails cannot be redirected or tagged at this stage (as they have not arrived yet, see the Filtering Points Concept for more information), but you can control the SMTP responses returned upon rejection. The response will be included in the Non-Delivery Report (NDR) generated for the actual sender, so they will be notified about the exact reason of the rejection.
Find the related configuration options under by clicking the Edit button under Before Arrival.
Click the three-dots (...) button next to the name of each test to edit the related SMTP response.
See the SMTP Responses section for more information.
Tarpit delay holds back SMTP responses sent by ORF upon blacklisting. As the sender server has to wait for the each response, you can use this feature to "fight back" spammers by slowing them down or to make it virtually impossible for them to carry out a successful Directory Harvest Attack (DHA).
For more information, please see the Tarpit Delay Settings section.
Enable this option to terminate the SMTP connection after returning the configured SMTP response upon rejection.
Some spam software attempt to send the email regardless of the SMTP responses. Though they do not succeed, they waste bandwidth. By closing the SMTP connection you can stop these software from continuing the SMTP conversation.
The SMTP standards do not specify clearly what the sender server should do if the connection is closed unexpectedly after an SMTP response indicating an error. Some email servers may interpret it as a temporary connection error and retry email delivery later. Some others may process the SMTP response and do not retry delivery.