Email Marketing – Techniques to Improve Inbox Deliverability

Email marketers care about the performance of their email campaign. Performance can be measured in many ways, including response, relevance, ROI, clicks, open rate etc. What is becoming increasingly clear to all email marketers, regardless of how they measure performance, is that the ability to deliver messages successfully to the recipient’s inbox plays a critical role.

Authentication is a cost-free, interoperable and easy way to guard against phishing and spoofing attacks. Authentication also increases the likelihood that emails will be delivered to the intended recipient and into their inbox. It is strongly recommended that anyone using email for marketing purposes adopt and use authentication protocols for both their email and corporate domains.

In addition to allowing users to block specific email senders, most ISPs partner with spam filtering companies with the goal of blocking unwanted email that displays characteristics of spam. Sender accreditation refers to a third-party process of verifying email senders and requiring them to adhere to accredited usage guidelines in exchange for being listed in a trusted listing that ISPs reference to allow certain email to bypass email filters. These lists use similar technology as block lists, but improve delivery from legitimate commercial senders.

A sender’s email reputation is determined by email recipients, ISPs, and other email monitoring organizations. ISPs rely on these collective opinions to determine reputation scores. The reputation score of a sender is a critical factor in determining whether ISPs choose to deliver their email to the inbox, the bulk folder, or not at all.

Protecting and Improving Reputation Score
As previously stated, reputation scores have a serious impact on deliverability. The following list of techniques protects and improves reputation scores.

Prohibit BCC
No commercial sender should send commercial email through any system that uses the cc or bcc field. There are too many opportunities for error if you are not using a mailing system that actually creates a separate message for each recipient, with only that recipient’s unique qualifying information it. Even the best companies can have processes go awry; therefore it is best to disallow using the CC or the BCC to send mass commercial emails.

Delivery Monitoring
Senders should monitor total delivery as well as inbox delivery. Total delivery can be measured by the difference between the number of messages sent and the number of bounced messages. While this method will not provide a good indication of what messages customers are seeing, as messages may be sent to junk folders, it will provide a good metric to be used in evaluating list hygiene.

Hygiene is the process of making sure your email list is accurate and up-to-date. This means removing addresses that have unsubscribed or are undeliverable for any reason. It also includes having good opt-in and opt-out processes so your subscribers can help you maintain the integrity of your database. Monitor the age of your database. Additionally, establish an on-going process for actively removing subscribers that are both old and inactive. Allow subscribers to easily change their email address on file with you – and use a consumer-reported Email Change of Address (ECOA) service on a quarterly or semi-annual basis.

Address Collection and Permission

  • Be clear about what you are offering the consumer. State the benefits, the content of the emails, the frequency and when the subscriber should expect the first email.
  • Keep permission current. Reach out to subsets of your file who are not opening or clicking every quarter or so. Ask if they would like to receive something different, or provide feedback on your email program.
  • Your address collection or hygiene process should reject or remove malformed addresses.
  • Your address collection or hygiene process should reject or remove abuse@ and postmaster@ addresses.
  • Your address collection or hygiene process should reject or remove role accounts (i.e.,
  • Your address collection or hygiene process should reject or remove email addresses containing profanity.
  • Provide an email preference centre for easy updating of email addresses.

Bounce handling
Email bounces are automatically generated messages that are sent from an ISP in response to an undeliverable message. Different email servers reply in different formats for the bounces they send back.

The major types of bounces are:

  • Hard bounces: A hard bounce indicates that an email cannot be delivered due to a permanent error (i.e. a mailbox that does not exist). Hard bounces should be removed immediately from a list or after a small number of consecutive hard bounces.
  • Soft bounces: A soft bounce is generated when an email cannot be delivered to an address due to a temporary error. A soft bounce indicates that it may be possible to deliver to the address at some point in the future. If an address bounces continuously for a period of time, it is recommended that senders remove the address from their lists.
  • Blocks: ISPs send bounce messages sometimes with a reason code describing why the mail was blocked. Senders have to make sure that these are handled differently from bounces and work with the ISPs to remove these blocks. The risk of not isolating these blocks is that legitimate email addresses would otherwise be tagged as bounces and removed from the list.

Defining Responsibilities
Although the roles and responsibilities of the initiators and senders of commercial email are established by CAN-SPAM, it is prudent to reiterate and further define these roles and responsibilities in a written contract governing the email marketing relationship.