Installation manual

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3.3.1 Microsoft Exchange Server
3.3.1.1 Transport Agent
In this section you can set up options for spam protection using the transport agent.
NOTE: The transport agent is not available in Microsoft Exchange Server 5.5.
When you Enable antispam protection by transport agent you choose one of the following options as an Action
to take on spam messages:
Retain the message - keep the message even if it is marked as spam
Quarantine message - send a message marked as spam to the quarantine mailbox
Delete message – delete a message marked as spam
If you want to include information about message’s spam score in its header, enable the Write spam score to the
header of scanned messages option.
The Enable Greylisting function activates a feature that protects users from spam using the following technique:
The transport agent will send a “temporarily reject” SMTP return value (default is 451/4.7.1) for any received email
that is not from a recognized sender. A legitimate server will try to resend the message after a delay. Spam servers
will typically not attempt to resend the message, as they usually go through thousands of email addresses and do
not waste time resending. Greylisting is an additional layer of antispam protection and does not have any effect on
the spam evaluation capabilities of the antispam module.
When evaluating the message source the method takes into account the configurations of the Approved IP
addresses list, the Ignored IP addresses list, the Safe Senders and the Allow IP lists on the Exchange server and
the AntispamBypass settings for the recipient mailbox. Emails from these IP addresses/senders lists or emails
delivered to a mailbox that has the AntispamBypass option enabled will be bypassed by the greylisting detection
method.
The SMTP response for temporarily denied connections field defines the SMTP temporary denial response sent to
the SMTP server if a message is refused.