1. Enter gateway routers from outside networks, process thru virus scanner.
   • Email enters our network and is immediately virus scanned using the latest definitions. If the email is clean, the process continues - otherwise the email is discarded and this process ends.
2. Verify against Directory Harvesting (DH Attacks).
   • Directory harvesting is the process of a spammer or spam robot (spambot) choosing random names and sending messages into the network, not knowing if the user really exists or not. The DNS Texas email system will not acknowledge these types of attacks. If a message inbound is destined for a non-existant account, the email is immediately discarded and this process ends. Legitimate emails pass through this filter and proceed to the next step.
3. Verify against Phishing URL Blacklists (PURLB).
   • Phishing is the process spammers use to lure you into thinking you've received email from a legitimate company, but the email may actually be forged and ask for personal banking information for verification purposes, etc. We successfully stop about 98% of such scams to protect our users. You should NEVER provide any banking details or personal details to anyone, unless you are sure the site asking for the information is legitimate and has the correct URL in the address bar! If an email is found to be a phishing scam, the email is quarantined. The sender will recieve an email stating the message was not delivered and this process ends. If email sender/address is not on PURBL lists, processing continues.
4. Verify against SPAM URI Blocklists (SURBL).
   • Global SPAM URI blocklists check every email entering this system again known bad sending URLs (whatever@address.com). This is quite an effective way to scan for SPAM emails since it doesn't matter what the content of the message is. If an address is found on the SURBL list, it means that sender has been identified as sending bulk or spam mails. If information in email is found on SURBLs, processing ends - the message is quarantined and since this process is nearly 99% accurate we do not send a delivery notification failure message. If message passes this check, it proceeds to next step.
5. Verify against local-allow Whitelists.
   • DNS Texas can whitelist addresses or domains - these address(es) do not process any further and are delivered to the users inbox at this time. Such qualifying items are friends who send emails with langauge or content that would normally be blocked, or critical communications between companies where spam filtering is not required and may hurt business if it blocks certain emails. DNS Texas will whitelist any legitimate email address upon request, pending it is in fact a good address. Email addresses/domains not on local whitelists will continue processing.
6. Verify against custom Blacklists.
   • Much like whitelists, blacklists do the opposite. These are local lists of domains or email address(es) that DNS Texas has identified as being bad senders/spammers. We have so far had about 99% accuracy with these lists. Any email sent from a domain/email address on this list is quarantined, a non-delivery notification is sent to the sender and processing ends. Emails/domains not on this local list proceed to next step.
7. Verify against Header Checking processes.
   • Header checking allows us to analyse email header information for bad information (missing or mal-formed fields usually caused by incorrect configurations of mail servers or spambots). DNS Texas actively checks the following header information on all inbound emails:
     • Empty 'MIME FROM' fields - Empty FROM: fields are normally a sign of incorrect configurations or SPAM bots.
     • Malformed 'MIME FROM' fields - Malformed FROM: fields are normally caused by incorrect configurations or SPAM bots.
     • Contains remote images only - Used to stop 'IMAGE ONLY' spams, where an email only contains a graphic (normally for such things as viagra).
     • Sending domain is valid (Reverse DNS Lookup) - RDNS lookup verified sender domain is legitimate and not made up.
     • Email contains any encoded IP address(es) - Encoded IPs are a binary version of a website name (instead of being http://www.address.com, the binary address might be something like http://100101011).
     • Email contains embedded .GIF image(s) - Embedded .GIFs are similar to 'Remote Images Only' - these are .GIF files (image files) that are embedded into the email. Some 'Smileys' and office outlook backgrounds use this method to show backgrounds, etc. However, spammers mainly use this to display graphic ads for products of all types.
     • Email contains .PDF attachment spam (.PDF attachments <25kb) - PDF (adobe acrobat) spam has recently taken off, since it is only an attachment, there is nothing for the spam filters to verify - this is a changing field at this time, but well over 95% of advertisment SPAM emails are <25kb in size. These attachments are blocked.
   • Important Note: DNS Texas does not accept emails with BLANK SUBJECT lines!
8. Verify against Sender Policy Framework (SPF).
   • SPF fights return-path address forgery and makes it easier to identify spoof emails (emails that are disguised as being from legitimate senders). Domain owners identify sending mail servers in their company DNS records. SMTP recievers verify the envelope sender address against this information and can accurately distinguish authentic messages from forgeries before any message data is transmitted. You can learn more about SPF by visiting [http://www.openspf.org]. If email passes this process, it continues - otherwise it is quarantined and a non-delivery message is sent to the sender.
9. Verify against global DNS Blacklists (DNSBL).
   • Global blacklists are 3rd party SPAM checking services that house lists of known bad domains that SPAM is or has originated from. Currently DNS Texas uses [SpamHaus] as it's primary DNSBL provider. You can check your sending blacklist status by visiting [SpamHaus]. You will need to check both the SBL and XBL lists. Note: DNS Texas does NOT maintain these blacklists. If email passes this process, it continues - otherwise, if is quarantined and a non-delivery message is sent to the sender.
10. Verify against local Bayesian Analysis databases.
    • The local bayesian database is a constantly learning 'smart' database. It learns what kinds of emails are legitimate from what our userbase sends outbound. By using this outbound information along with a known, ever updating database of bad emails, it can accurately determine if an email is legitmate or not. If email passes bayesian analysis, it continues processing - otherwise, processing ends and a non-delivery message is sent to the sender. [Learn more about bayesian filtering here].
11. Verify against local keyword databases.
    • Local keyword lists are lists of known bad words, sentences or content in the message subject or body. These lists are maintained by DNS Texas system administrators. If an email passes these checks, processing continues - otherwise, message is quarantined and a non-delivery message is sent to the sender.
12. Message is delivered to user inbox.
    • After successful processing of the above steps, the clean email is delivered to the recipients inbox. No further processing is performed.

This Is The SPAM / VIRUS Firewall At DNS Texas. Your Recent Message Did Not Reach Some Or All Of The Intended Recipient(s).

To: [Recipient email/name]
Subject: [Subject Line You Entered]
Sent: [Date]

Server: mx#.dns-tx.com (25.12.# - SPAM/VIRUS FIREWALL - REJECTED)

There are several quick things you can do in this case - the following information is provided to assist you in correcting the problem:

• Verify the email address you are sending to is valid and contains no typos!
  • An invalid address triggers the 'Directory Harvesting Rule (#2)' listed above.
• If you are sending from a non-personal account, such as from your work location you can:
  • Ask your system administrator to verify your domain has not been blacklisted on the SpamHaus RBL lists. Removal of your domain off of this list is handled via the [SpamHaus website]. Domains found on this list invoke the 'DNSBL Rule (#9)' listed above.
• If you are sending from a non-business account, such as your home email, please:
  • Verify you have your email program setup correctly! Incorrect or bogus information entered in the email program setup can trigger the 'Header Checking Rule (#7)' listed above.
  • Also make sure your email has a valid subject line - our system does not accept emails with blank subject lines.
• Check content!
  • 'Keyword Database Rule (#11)' listed above aggressively checks for questionable quotes, words or sentences in both the message body and subject! This material may include keywords such as: mortgage/re-finanace offers, stock or penny stock emails, pen*s or bre*st enlargements, incredible software deals, male/female body part references, certain offensive language, etc.

• The name of the person you are trying to reach
• The email address of the person you are trying to reach
• The approximate date/time the email was originally sent
• Your email address
• A copy of the returned email/spam filter bounce-back email (if available)

Optionally, you may send a copy of the e-mail you are having trouble getting delivered to the DNS Texas NO-SPAM robot for review. This is a manually reviewed account where servicing technicians will route the e-mail in question to the appropriate user and white list as needed. Submission to the DNS Texas NO SPAM robot eliminates the need to call support or e-mail support to report delivery issues. The NO SPAM account is checked regularly throughout the business day. Submit blocked e-mail to the following address for review/whitelist: nospam@dnstexas.com

Having this information will allow us to quickly identify why your email was stopped and help up prevent false-positives in the future. The DNS Texas helpdesk is available during [normal business hours] and can be reached via the following method(s):

• { WEB: http://www.dnstexas.com }
• { EMAIL: support@dnstexas.com }
• { PHONE: (682) 365.2643 }
• Coming Soon: Web Form Unblock Requests

Interested in SPAM protection for your own mailbox? DNS Texas may be able to help!
Learn about our [SPAM filtering] and [3rd Party SPAM filtering]