Editor’s note: New authentication methods and stricter filtering standards are hurting e-mail deliverability rates. In the first in a continuing series, Schwedelson, corporate vice president of Boca Raton, FL-based list services firm Worldata, will explore how you can reach your audience despite the ever-increasing obstacles.
By and large, people who have e-mail accounts want to receive less irrelevant e-mail. Internet service providers (ISPs) and e-mail service providers (ESPs) are responding to their clients’ (your audience’s) desire for a cleaner e-mail inbox with content filtering, blacklists, and blackholes.
Just as the ISPs and ESPs are constantly monitoring e-mail and e-mail senders, you need to constantly monitor your e-mail marketing campaigns to be sure that they are reaching the intended audience—and that the intended audience does indeed welcome the messages. Identity management and whitelists are a couple of ways that marketers can help their e-mail pass ISP and ESP scrutiny. Identity management can include Sender ID, DomainKeys, and E-mail Accreditation. These solutions strive to assure e-mail recipients that the sender is actually who he purports to be and that he wants an open and responsible marketing relationship.
Sender ID is a mailer verification method offered and used by Microsoft. An e-mail sender publishes a Sender Policy Framework (SPF) record for each domain that he uses to send e-mail. This record carries the IP addresses of the authoritative e-mail servers for the domain.
When e-mail is received, the receiving server looks for the SPF record in the domain name server (DNS) for the domain specified in the e-mail “from” field. It then compares the IP address from where the e-mail was received to the IP addresses specified in the SPF record published in the domain’s DNS. If the sending IP address matches one of the IP addresses published in the SPF record then the receiving e-mail server considers the e-mail as being validly sent from the domain.
Microsoft is using Sender ID within its Hotmail e-mail service. When Hotmail’s receiving e-mail servers cannot find a valid SPF record, Hotmail will include a yellow highlighted message at the top of the e-mail message indicating that the sender could not be verified. If the sending IP address does not match an authoritative IP address that is published in the SPF record, then Hotmail will deliver the e-mail message to the user’s junk folder.
DomainKeys is Yahoo!’s method for evaluating an e-mail message and determining when it is genuinely being sent by the domain in the “from” field. DomainKeys relies on providing a digital signature for every e-mail that is sent. To digitally sign the e-mail, the sender must first obtain a public and private key pair based on the Public Key Infrastructure (PKI). The public key is published by the e-mail sender in the DNS for each of the sending domains. The private key is used by the sender to digitally sign the e-mail message based on its content. Therefore, the sending e-mail server software must have the ability to construct a digital signature for each e-mail message it sends.
When an e-mail is received, the receiving server looks into the DNS records for the sending domain and retrieves the public key if it is published. The receiving e-mail server can then use the public key to check if the digital signature was produced by the corresponding private key that the sending server used to produce the digital signature. Thus, the receiving e-mail server will be able to verify that the e-mail message was sent from the domain specified in the e-mail “from” field.
Digital signatures are created and checked by using a hashing algorithm developed by cryptography experts. The algorithms must be run each time an e-mail message is sent and each time one is received. All of the cryptographic hashing increases the amount of time it takes to send an e-mail and increases the amount of processing needed as well.