Administrator's Guide - Kerio Software Archive

Chapter 16 Antispam control of the SMTP serversages while the From and To rules are tested against From: and To: headers includedinside the message.The issue will be better understood through the following examples:• Example 1:In Example 1 (see table 16.1), rules are ordered so that messages sent fromjwayne@spammer_domain.com are accepted by Kerio MailServer, while any other messagesfrom the spammer_domain.com domain are blocked on SMTP level. The thirdrule allows any messages delivered to the local domain company.com on SMTP level.Warning: The following testing methods are applied prior to custom rules:• Spam repellent• Caller ID and SPF• Whitelists/BlacklistsThis, however, implies that every message including thejwayne@spammer_domain.com address as a sender is tested. If not blockedby the tests listed and having reached custom rules, the permission rule is appliedand no additional tests will be applied to the message (actually, they will, but theirresult scores will be set to 0 points).Header Type Content ActionFromAddress jwayne@spammer_domain.com EnableFrom Domain spammer_domain.com DeclineTo Domain company.com EnableTable 16.1 Example 1:• Example 2Example 2 (see table 16.2) shows a situation where any email addressed toadmin@company.com is blocked on SMTP level. The next rule blocks any email fromthe spam.com domain except messages where the test string is included in theSubject header.Header Type Content ActionTo Address admin@company.com DeclineSubject Substring testEnableFrom Domain spammer_domain.com DeclineTable 16.2 Example 2Warning: The examples imply that, when creating rules, it is also necessary to avoidsituations where one rule is unexpectedly influenced by another. This might happen forexample when users are subscribed in mailing lists and addresses in MAIL FROM: andRCPT TO: do not match addresses in From and To headers inside the message.180