Page 47 - Mercury Manual.book

Mail Filtering Rules 42
How mail filtering works

Rules that always trigger (the Always triggers button) This creates a rule that has no condi-
tions and always triggers. You will most commonly use this type of rule in conjunction with
flow control actions (see later in this section).

Message size matching (the Size button) Allows you to create a rule that triggers based on
the size of the message. Enter the size you want to check, and whether the rule should trigger
when the message is smaller or larger than that size.

Message attributes (the Attribute button) Allows you to trigger a rule depending on certain
identifiable characteristics of the message. Select the attributes that should trigger the rule by
checking any of the boxes in the editor dialog. Note that the rule will trigger if any of the con-
ditions you check is true. If you want to check for messages that contain multiple attributes,
you should check for each attribute and connect the rules using a Logical AND operator rule
action (see below).

List membership scan (the Scan list button) creates a rule that triggers if the sender of the
message is a member of a specified distribution list (see the section later in this manual for
more information on distribution lists). You can use this type of rule to control access to your
mailing lists (for instance, by allowing only list members to post mail to a list); you can also
use it to control spam, or unsolicited commercial e-mail by adding known spam addresses to
a distribution list then checking it before you accept mail for delivery. When you create the
rule, simply type in the name of the distribution list Mercury should search, and it will do the
rest (note: you should enter the name of the list as it appears in your "list of lists" file, without
a domain). You can tell Mercury to scan a plain text file instead of a Mercury mailing list by
entering the special character '@' followed by the full path to the file.

List scan rules have two major applications:

1. Creating "kill" files to catch "spam" (Unsolicited Commercial E-mail) from known
See the chapter on the addresses. When you receive an unsolicited spam message, you can add the sender's
MercuryS SMTP Server
for information on other address to a list of known evildoers, then delete all future messages from that address
ways of blacklisting known using a single rule of this type.
spammers and their sys-
tems.
2. Verifying that a person is a list member: if you offer services that are triggered by filter-
ing rules (for instance, if you return product information or encryption keys in response
to automated messages), then you may wish to verify that the person sending the request
is actually a member of a list of authorised people before providing the service. You can
use a rule of this type to determine whether or not the person is authorised based on their
membership of a list.

Advanced option – matching whole domains: You can create an entry in your target distribu-
tion list that matches any address from a single domain by editing the list manually and add-
ing a line exactly like this:

\MATCH *@domain.com
The "\" character must appear hard against the left margin of the file.

Example: to suppress all mail from any address within the domain "bigdeals.com", you
would add the following line to your distribution list:

\MATCH *@bigdeals.com