DAWKCoTM SMTP Rules Component integrates with Windows® IIS SMTP Service1 to regulate inbound e-mail traffic per admin policy. It controls whether certain inbound SMTP protocol commands are accepted or blocked in order to: block spam; defend against phishing, hacks and exploits; and, block non-deliverable inbound messages to eliminate "Badmail".
The Software package includes the SMTP Rules Component (a COM Automation Type Library DLL), an Admin Utility program for applying rules settings to IIS SMTP Virtual Server instances, and a detailed Help file, including context help linked to the SMTP Rules Admin program.
For details, see the Help File.
See also: Customer Feedback
Notice: we do not provide any Blacklist, Block List or Blackhole List services. Our software component makes decisions about blocking inbound e-mail based on query responses received from DNSBL servers regarding the IP addresses and/or domains of connecting computers. If your IP address, or that of your domain or e-mail server, has been put on a blacklist or is being blocked, you should visit the web site of the DNSBL server operator to learn more about why, and to find out how to get delisted.
Purpose of the SMTP Rules Component
The DAWKCo SMTP Rules Component will control whether specific inbound SMTP protocol commands are accepted or rejected (blocked), based upon rules that are set by the mail system administrator. With respect to the IP addresses and/or domains of all inbound SMTP connections, its spam blocker will implement and enforce rules for the following tests:
- Reverse and Forward DNS Lookups
- Multiple IP-based and/or Domain-based DNSBL (Block List) Queries
- Sender (MAIL FROM) Domain Mail eXchanger or Host DNS Lookups
- DNSCCL (Country Codes List) Queries checked against a locally defined Country Codes Block List file
- URIBL message scanning
These measures provide anti-spam protection through connection blocking and message rejection, as well as defense against phishing, hacks and exploits perpetrated by Internet abusers. Additionally, the SMTP Rules Component can perform local POP3 mailbox lookups2 to eliminate non-deliverable inbound message traffic. The primary uses for the component are to:
- Block Spam
Query one or more IP-based and/or Domain-based DNSBL (Block List) servers that you specify and block inbound e-mail connections from known spammers*, phishers, hackers and abusers. *Senders of UBE/UCE or Unsolicited Bulk/Commercial E-mail.
- Reject Spam
URIBL scan all messages and reject spam e-mail messages that contain URI links to hosts listed on any of the DNSBL servers specified.
- Minimize Hack & Exploit Attempts
Require correct Reverse and Forward DNS resolution of all connecting host IP addresses. Require DNS resolution of a Mail eXchanger (or Host) for all Sender (MAIL FROM) domains. Optionally, block all connections originating from countries that you specify.
- Reject Non-deliverable Incoming E-mail
Verify Local Recipients using a DAWKCo POP3 Server configuration and block transmission of mail to invalid mailboxes, disabled mailboxes and mailboxes that are over quota.2
- Reduce Badmail
Eliminate Badmail due to non-deliverable DSN's (bounces) by blocking non-deliverable inbound e-mail.2
Features of the SMTP Rules Component
The DAWKCoTM SMTP Rules Component implements the IIS SMTP Service Events Architecture and Windows Server Extension Objects to provide enhanced SMTP inbound protocol command handling for IIS SMTP Virtual Servers. The component is a high performance ATL-based COM (Component Object Model) Automation Type Library DLL (Dynamic Link Library) with the following features:
- Fully synchronized Free Threaded (Multithreaded) operation maximizes multiprocessor performance.
- Object Caching and reuse eliminates object instantiation/destruction overhead.
- Coded entirely in C++ for optimal speed, efficiency and compactness.
- Rigorous C++ exception handling provides robust, rock solid operation.
- Gracefully defers control to the IIS SMTP Service in the rare case that an event is not handled.
- Simple to use SMTP Rules Admin program with comprehensive Help makes applying and removing SMTP rules to/from SMTP Virtual Server instances a snap
- Supports the use of optional IP Address/Subnet Exceptions and Domain Exceptions list files so that you can unconditionally allow all e-mail traffic from the specific IP addresses/subnets and/or domains that you choose.
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e-Mail Server Protection Provided By ZEN (Zen.Spamhaus.Org):
Spamhaus Block List (SBL), Exploits Block List (XBL),
Policy Block List (PBL) & Register of Known Spam Operations (ROKSO)
The Spamhaus Project DNSBL server (actually, currently 40 mirrored servers in 16 countries worldwide) was selected as the first default* DNSBL server for several reasons. (*Can be overridden.) The Spamhaus Project is world renowned for its anti-spam efforts and tools. The Spamhaus DNSBL servers are used to protect e-mail servers by most of the largest Internet Service Providers, as well as corporations and government agencies (e.g., the FBI). In most cases, use of the Spamhaus DNSBL is free of charge*. (*Very large scale operations must subscribe to the service and use a live "Data Feed" to implement the blocking list database locally). To quote the Spamhaus mission statement from their website:
"Spamhaus is an international non-profit organization whose mission is to track the Internet's Spam Gangs, to provide dependable realtime anti-spam protection for Internet networks, to work with Law Enforcement Agencies to identify and pursue spammers worldwide, and to lobby governments for effective anti-spam legislation."
To protect networks and email users, Spamhaus publishes three spam-blocking databases: the Spamhaus Block List (SBL), the Exploits Block List (XBL) and the Policy Block List (PBL).
The other default IP-based and Domain-based DNSBL servers were selected because, in most cases, they catch any spam sources that the Spamhaus Project servers miss.
During trials, and subsequent production environment operation on DAWKCoTM Software e-mail servers, the DAWKCo SMTP Rules Component effectively blocked over 99% of all incoming Spam and virtually eliminated all "Badmail" due to non-deliverable DSN's or bounces*.
*Badmail messages are messages that are deposited in the SMTP Badmail folder due to routing/delivery failure. Note that the elimination of Badmail messages was largely dependent on the optional Verify Local Recipients... feature, which in turn depends on a coexisting DAWKCo POP3 Server installation.2
"By the way...for some reason my domain was targeted by a huge increase in spam, but I didn't notice until I looked at the [SMTP Rules Component] logs and [saw]...Thousands of spam mails have been blocked ... don't know what is happening but it's saved my mail system from being overwhelmed...hence, the reason I just put it on a customer server, and in [several] days [it] has...blocked over 2,000 [Spam messages] and I lost count somewhere [over] 20,000 in 3 months [on my system] -- the [SMTP Rules Component's] reverse DNS has been switched back on...and this reduced the contents of my junk mail folder by 100 a day.
Millennia Computer Services Ltd
Requirements for the DAWKCo SMTP Rules Component
- Microsoft® Internet Information Services (IIS) version 5.0 or later (32-bit), which is included in the following Windows® 32-bit operating systems: 2000, XP, 2003, Vista, 2008, or later (Professional, Business or Server versions)3.
- Optionally, the Verify Local Recipients... feature requires either: DAWKCo POP3 Services Small Business Version 5 or later, or POP3 Server Hosting Version (with or without the WebMAIL Extension)4.
1 and 2: see the Requirements above.
3 XP Home version is not supported. Vista support requires a version that includes the IIS SMTP Service (e.g., Vista Business).
4 The SMTP Rules Component will work either with, or without, a DAWKCo POP3 Server installation, but the usefulness of the SMTP Rules Component is enhanced when there is a coexisting DAWKCo POP3 Server installation2; specifically, non-deliverable message traffic can be virtually eliminated by using POP3 mailbox lookups to verify addresses specified in "RCPT TO:" commands during SMTP sessions.
Tech Support for the SMTP Rules Component
Free* phone and e-mail tech support is available for DAWKCoTM SMTP Rules Component software installation and setup issues. *Limitations apply--see your license agreement.
Please see our Tech Support page for support contact info, the support FAQ, help with Setup and Known Issues, Example Screen Shots, and a search tool for Support Inquiry Response (SIR) articles.
MD5 Credits: portions of the DAWKCoTM SMTP Rules Component, POP3 Server & MailDaemon, WebMAIL and Admin API software programs contain code that implement encryption, decryption and the CRAM-MD5 authentication mechanism derived from the RSA Data Security, Inc. MD5 Message-Digest Algorithm, copyright ©1991-1992 RSA Data Security, Inc.