Eliminating e-mail addresses that are no longer valid is crucial, Listrak says.

Most e-mail marketers measure open- and click-through rates to gauge the effectiveness of their e-mail marketing campaigns. But too often they overlook factors that reduce the percentage of e-mails that make it into a recipient’s inbox, says Megan Ouellet, marketing director of Listrak, a provider of e-mail marketing services.

In a new Listrak white paper, “From Acquisition to Win Back: E-mail Deliverability Tips for Every Stage of the Customer Lifecycle,” Ouellet notes that the major providers of e-mail addresses to consumers are increasingly focused on rewarding good e-mails by ensuring they land in consumers’ inboxes rather than just blocking bad e-mail. (Those e-mail providers, such as Yahoo Inc., Microsoft Corp. and Google Inc. are typically called Internet service providers, or ISPs by e-mail marketing experts.)

In the past, for example, ISPs were more likely to block a high percentage of a sender’s e-mail if some of its recipients clicked their spam button. But now if that same sender also takes proactive steps to show its e-mail is legitimate and engage recipients, ISPs are more likely to deliver a higher percentage of e-mail to the inbox even if some recipients are hitting the spam button, Listrak says. But senders still need to ensure they’re taking the right steps that result in better treatment from ISPs.

“While this is helping to reduce the number of legitimate messages from being delivered to the junk folder, it’s tough for ISPs to know the good senders from the bad,” Ouellet writes. “So it’s up to the sender to ensure that the right factors are in place.”

Sender reputation, she adds, “remains the cornerstone of deliverability.”


To help marketers understand key steps they need to ensure their e-mails arrive, Listrak lists, in order of importance, the following factors ISPs consider in scoring a sender’s reputation.

Invalid addresses—E-mails that bounce because they were sent to invalid and inactive e-mail accounts.

User complaints—Recipients click the Report Spam button because they don’t recognize the sender, they don’t remember opting-in to a marketer’s list, the content of the message is no longer relevant to their needs, they don’t like the sender’s e-mail frequency, or they want to unsubscribe from the sender’s list.

Domain—Most ISPs augment their IP-based reputation systems with domain-based reputation services that rely on DK/DKIM, or DomainKeys/DomainKeys Identified Mail, which is used to validate the domain name associated with an e-mail message. Under the DK/DKIM system, ISPs can check the coding a sender places in the e-mail header with information the sender has registered with the Domain Name System, to ensure that the e-mail is being sent from the sender’s web address. This is used to guard against e-mails that, for example, may be sent by criminals who attempt to use variations of legitimate domain names in phishing attacks that lure consumers into revealing confidential information like credit card account passwords.  


Frequency—ISPs favor senders whose frequency follows regular patterns. Sending too frequently or infrequently will damage a marketer’s reputation.

Volume—Sudden bursts of high volume can lead to penalties. Marketers should segment their e-mail lisst into small groups and stagger delivery patterns so that all e-mail marketing messages don’t hit ISPs at the same time.

Size—E-mail messages should be 10 to 60 kilobytes and never include attachments.

Content—Even though ISPs’ text filters are not as strong as they once were, words such as “free” can prevent an e-mail message from getting delivered, especially if the other tips on this list are not followed.


Third-party reputation services—ISPs rely on certification and accreditation services to vouch that a sender is legitimate.

Engagement—ISPs monitor the number of recipients who open and click on a sender’s e-mail messages, along with the number who ignore or delete the sender’s messages. Thus, sending messages to inactive subscribers can hurt a marketer’s reputation and deliverability rates.

Spam trap hits—So-called spam traps are old e-mail addresses that their users have abandoned. ISPs monitor these e-mail addresses even though no one uses them, and sending to these addresses results in a lower effective delivery rate for the marketer.

Sending infrastructure—Marketers can help to maintain good reputations with ISPs by sending e-mails compliant with RFC standards and ensuring content and links are not misleading or otherwise inappropriate. RFCs, or request for comments, is shorthand for rules for e-mail and other Internet-related operations.


Listrak has two clients listed in the Internet Retailer Top 500 Guide. Additional e-mail services providers can be found in Internet Retailer’s Leading Vendors to the Top 1000 E-Retailers.