Setting Up the Sending Email Gateway (Email Server)
As Internet service providers build countermeasures to spam, it becomesincreasingly difficult for reputable email senders to deliver email.Major ISP's are simply attempting to force senders of email intotheir servers & gateways to be accountable for that email. Theyare protecting their customers and allowing their customers toprovide feedback to better serve them.
The following items are required before you send any mass email throughyour gateway. If any of these items is not in place before you send,despite a likely return on investment, you will damage yourreputation and brand name on the first email and continue to do so astime goes by. This will cause additional resources and cost to repairthe brand damage caused by a rush to produce a small ROI at any cost.
MX Record and Reverse PointerAn email message is sent in an envelope. The envelope from always usesyour sending domain, while the message from header may contain anydomain. Other mail servers will use the domain found in the envelopefrom to look your mail server up and send feedback in the form ofdelivery status notifications (bounces). If no mx record is found forthe domain, many gateways will drop the connection.
The mx record is simply 2 lines added to your DNS records file.mydomain.com. IN MX 5
mail.mydomain.com.
mail.mydomain.com. IN A 12.96.120.123
The first line specifies the mail exchanger to use and the secondprovides the ip for that mail exchanger. There may be multiple mailexchangers in an mx record. This is a built-in load balancing andfailover mechanism for smtp. The preference is an integer thatappears after the MX and before the mail exchanger name. It specifieswhich mail exchanger to try first.
Once a mail server has looked up your mx record, it may also want to lookfor a reverse pointer for the ip in the A (address) pointer to makesure you're not spoofing the domain. Some gateways only check that areverse pointer exists for the ip. Others require that the reversepointer name and mail exchanger name match. The following articleshould help you create your reverse zone and pointer.
http://www.apnic.net/db/revdel.html
Implement Sender Policy FrameworkWhile this is optional, implementing sender policy framework for yourdomain will save you the time and trouble of filling out forms thatrequest the same information and can improve deliverablity to somegateways. You'll only need to add an Internet class text message toyour zone record file. This record tells other gateways what ips you sendmail from. They can use that information to protect against domainspoofing. You can learn more about spf at
http://www.openspf.org/.
The following is an example spf record.
mydomain.com. IN TXT "v=spf1mx ptr ip4:12.96.182.128/27 ~all"
Implementing Domain Keys
Implementing Domain Key signatures for all your mail is entirely optional at thistime, but may not be for long. Domain Key signatures are implementedby your mail server and your DNS server. XMS supports domain keys.Check the documentation for details on implementing domain keysignatures. A message signed with domain keys and verified by thereceiving gateway is certain to originate from that domain.
Handle FeedbackHandling feedback from other gateways is mandatory today. If you fail to acton feedback, your domain will quickly be blacklisted and you'll beforced to fill out some more forms to correct the problem. Somegateways will not even grant initial access unless they can verifydeliverability to key addresses for feedback. Bounces are deliveredto the address used in your envelope from, but there are otherrequired addresses, that include
postmaster@mydomain.comand
abuse@mydomain.com.Many gateways will monitor your reaction to feedback. If you attemptto deliver to an address reported to be bad at a gateway more thanonce, you'll decrease your reputation score at many gateways and findit more and more difficult to deliver mail there. Negative feedbackcontained in bounces can include bad addresses, spam complaints andattempts to unsubscribe. Your gateway is responsible for creatingscripts that remove these addresses from all distribution lists.
Implement a Double Opt-In Subscription PolicyYou must verify the intention of any user subscribing to a list. If youdon't, others will intentionally or unintentionally add trapaddresses or addresses that generate spam reports to your lists.Since not all gateways return the original recipient of a spamcomplaint and trap addresses return no feedback, it's very difficult,if not impossible to remove these addresses after the fact. A spamtrap is an address that is created, but never subscribes to anylists. For any message delivered to a spam trap, the sending ip isadded to a spam database.
