Anti-spam tool for Exchange 2000 server / IIS SMTP Service.
Windows All Versions
Open Relay Filter is a high-performance spam filtering extension for Microsoft? IIS SMTP Service and Microsoft? Exchange? 2000/2003 servers.
The Enterprise Edition is a very flexible and robust solution for reducing or eliminating the spam hitting your server.
Open Relay Filter Enterprise Edition runs as a service and integrates with IIS SMTP Service using its Open Relay Filter SMTP Module..
How does it work?
Open Relay Filter builds into the SMTP conversations and monitors the incoming email traffic of the SMTP Server. When Open Relay Filter detects that the incoming mail is a spam it rejects the mail by rejecting either the sender or the recipient(s) of the email.
This is a brief introduction of the features provided by Open Relay Filter Enterprise Edition.
; Protocol level protection
Spam is blocked on SMTP protocol level by refusing either the sender or the recipient(s) of the incoming email.
; Always up-to-date software: DNS blacklists
Open Relay Filter's most effective spam filtering feature is the ability to use multiple external spam source databases (DNS blacklists) simultaneously.
Open Relay Filter is shipped with dozens of DNS blacklist definitions and the list can be extended.
Most of these DNS blacklists, like SpamCop or ORDB are updated almost every second which guarantees that Open Relay Filter can block even the most up-to-date spam attacks.
; Custom tests: Reverse DNS, FQDN test...
For the most effective filtering Open Relay Filter also offers custom tests in addition to the DNS blacklists usage.
The reverse DNS (RDNS) test can reject emails coming from fake, non-existent domains, the FQDN test is for blocking emails with broken sender information.
; Reject mails for unknown recipients
Unlike other mail servers, Exchange 2000/2003 does not reject mails coming to mailboxes that does not exist. Exchange 2000/2003 accepts the mail for delivery and bounces the email later if the recipient mailbox is unavailable. Spam is often sent with fake sender email address that does not exist to recipients that are no longer valid, which results in tons of NDR's filling up the mail queue.
Using the Open Relay Filter's Active Directory integration you can reject all mails that are addressed to mailboxes that are no longer (or never been) valid and accept mails only to mailboxes that exists in the Active Directory.
; High-performance filtering with low resource usage
Open Relay Filter was designed with high-performance and robustness in mind. We have built in a configurable DNS cache that can store DNS lookup results. This saves you bandwidth and increased throughput because the same DNS lookup does not have to be performed twice.
Unlike spam content filters, Open Relay Filter utilizes virtually 0% processor time, because it does not do to many processor and memory-intense string operations.
Open Relay Filter performs well even under heavy usage. It is being used in networks with a daily average of half-a-million incoming mail without any performance problems.
; IP, sender and recipient blacklists/whitelists
You can create your own IP address, sender and recipient email address lists. While the whitelists can be used to exclude hosts, senders or local mailboxes from filtering, the same type of blacklists help you reject messages from specific hosts or IP ranges, senders (domains) or local mailboxes.
The IP addresses can be specified using direct definitions (the IP address itself) or by using subnet mask.
The sender/recipient whitelist also supports using masks to specify the email address to be whitelisted.
; Monitoring Open Relay Filter
Open Relay Filter produces detailed, customisable logs about both verified and rejected mails. Real-time statistics are also available.System requirementsMicrosoft?Windows?2000/2003; Microsoft?IIS SMTP Service must be installed (IIS 5 or 6); Microsoft?Internet Explorer?6 or later; 4Mb (megabytes) of hard disk space for program and help files; Administrator privileges to install and configure
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