Defending Against Active Attacks - IBM AH0QXML - Lotus Domino Messaging User Manual

spammer marks the e-mail address as a valid target for spam. This type of attack
simulates the transmission of an e-mail with a large list of recipients. This
harvesting technique is especially effective for spammers when you configure
Domino 6 to validate recipient addresses during transport by enabling the "Verify
that Local Domain Recipients exist in the Domino Directory" setting in Inbound
do not
Intended Recipient Controls. For this reason, we recommend enabling this
setting since it can assist spammers in targeting your domain for spam. However,
if you must use the setting, you can reduce the effectiveness of this type of
address harvesting by using the Domino 6 ini setting . The
SMTPMaxForRecipients setting will not stop harvesting, but may slow it down or
reduce it. The intention of the SMTPMaxForRecipients ini setting is to prevent
messages with large lists of recipients, but it has the useful side effect of making
it a little more difficult for spammers to harvest addresses.

4.5.4 Defending against active attacks

We recommend that you configure Domino to hold undeliverable mail. This can
be done from the Configuration Settings document, under Router/SMTP
Advanced Controls. Change the value of the field "Hold undeliverable mail" to
Enabled. The field is located in the Additional Controls (Delivery and Transfer)
section shown in Figure 4-23.
Figure 4-23 Undeliverable mail setting
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Chapter 4. Domino 6 Server anti-spam features