Diablo Analytical Unsolicited Bulk/Broadcast E-Mail Policy

Unsolicited Bulk/Broadcast E-Mail (referred to as "UBE" or "spam") is threatening to destroy e-mail as a communication medium for both individuals and businesses. At times, 80-90% of the connections to our mail server are unsolicited and are in many cases, abusive. We don't undertake the expense of hosting and managing an e-mail system for the purpose of providing free distribution of unsolicited junk mail. However, that is exactly what is happening.

As a result of these attacks on our company's network resources, we have been forced to implement technology to identify and block spam and other abusive activity. Although we try to use "low risk" blocking techniques, legitimate messages are occasionally incorrectly classified as spam and are blocked by our system.

If you feel that we have blocked a legitimate message or want to request that we "whitelist" your IP address, please contact us at administrator@diabloanalytical.com. If your domain is currently being blocked by our system, you can contact us via our web-based helpdesk or by phone: (925) 609-1150.

Important: We will generally unblock or "whitelist" an IP address without question if contacted by a live human being. However, whitelisting/delisting will be revoked without notification if abuse is subsequently detected from that IP address (or for any other reason we deem at our sole discretion to be justified - our mail server, our rules).

Reverse DNS (rDNS) Required

We require all mail hosts that connect to our SMTP server to have Reverse DNS defined. If your mail server does not have a PTR record that returns a valid rDNS response, then you will likely receive a "failure notice" from your mail system that includes an error description similar to the following:

> 501 5.7.1 Sender IP must resolve

Automatic Blocking - DNSBL

Diablo Analytical currently uses several "low risk" Domain Name Server style Blocking Lists (DNSBLs) including, but not limited to:

The SpamHaus "Zen" DNSBL, which lists known spam sources, insecure hosts, and dynamic net blocks that shouldn't host a mail server: http://www.spamhaus.org/
The SpamCop DNSBL, which lists hosts that have sent UBE to SpamCop users or spam traps: http://www.spamcop.net
The Distributed Server Boycott List, which lists open proxies and open relays that have been used to deliver spam: http://dsbl.org/main

You will have to deal with these organizations directly if you have been placed on their lists. Diablo Analytical has absolutely no control over who is added to or removed from these lists.

If your message is blocked because of a DNSBL listing, you will likely receive a "failure notice" from your mail system that includes an error description similar to the following:

> 501 5.7.1 ... Sender refused by the DNSBL zen.spamhaus.org (see http://www.diabloanalytical.com/ube.htm)

Note that IP addresses that are blocked by a DNSBL listing are automatically added to our "Intrusion Prevention" list, which will block delivery to our mail server for an additional period of time (see "Intrusion Prevention: below).

Please note that if you, your company, or your ISP have been listed on any of these DNSBLs as a spam source, open proxy, or open relay, then you have serious security and/or mail policy issues that should be dealt with immediately. You can use the "DNS Stuff" web site (http://www.dnsstuff.com) to generate a blocking list report for the IP address of your mail server.

Intrusion Prevention

If our mail server detects certain kinds of suspicious or abusive activity, the offending IP address may be blocked temporarily. In this case, you will likely receive a "failure notice" from your mail system that includes an error description similar to the following:

> 421 4.0.0 Intrusion prevention active for [IP Address]

IP addresses listed in the Intrusion Prevention list will eventually age off the list automatically.

Note: IP addresses that were blocked by one of the DNSBLs are automatically placed on the Intrusion Prevention list to reduce DNS lookups to the DNSBL when subsequent attempts are made to deliver mail to our server (spammers often don't take "no" for an answer).

Spam Filtering

Diablo Analytical also uses sophisticated filters that analyze message content in order to identify and block likely spam messages.

If your message is blocked by our spam filter, you will likely receive a "failure notice" from your mail system that includes an error description similar to the following:

> 554 5.7.1 Content filter rejection - Spam Characteristics (see http://www.diab.com/ube.htm )

Blacklist/Rules Filter

Diablo Analytical maintains a local "blacklist" of IP addresses that have been used to abuse our mail system. This abuse includes the delivery of UBE to one of our users. Blacklisted IPs have access to our system permanently blocked.

If your message is blocked by our rules filter, you will likely receive a "failure notice" from your mail system that includes an error description similar to the following:

550 5.7.1 <...> Access to <...> not allowed by rules

Firewall

Particularly abusive IP addresses may be added to our mail server's firewall list. If your message is blocked by our mail server firewall, you will likely receive a "failure notice" from your mail system that includes an error description similar to the following:

> 550 5.7.1 < ... > Permission denied

In rare cases, in order to stop continuing abuse we are forced to add IP addresses to the deny filter on our border router. In this case, that IP no longer exists on our version of the Internet.

Dangerous Attachment Rejection

Diablo Analytical rejects e-mail messages that contain attachments with potentially "dangerous" file types that can be used to distribute viruses, trojan horses, worms, etc. If you have a valid reason to send one of these file types to one of our users, please contact our mail administrator.

Virus Scanning

All messages entering and leaving the Diablo Analytical e-mail system are scanned for viruses. Any message containing a virus will be blocked.