A jargon free introduction to the world of email delivery
Blacklist. A list of senders or URLs (i.e. links) known or believed to be associated with spam.
Organizations use their own or third-party blacklists to quickly tag incoming email from a blacklisted sender (or featuring a blacklisted URL) as spam. Such messages are commonly deleted or subjected to closer scrutiny before delivery.
Read more about email blacklists and how to know if you're on one.
Email authentication. The processes, standards and technologies involved in verifying the identity of an email's sender.
Email that can be authenticated is less likely to be treated as spam.
Email certification. The process where a third-party agency audits the email practices of a sender and, if the sender meets the appropriate standards, gives them a virtual stamp of approval.
Certification agencies have agreements with various ISPs, webmail services and anti-spam technology providers that grant email from certified senders priority treatment.
Certified email is more likely to get delivered by these partners and may also receive other benefits (such as never having images blocked from displaying).
Feedback loop. A subscription service offered by organizations managing email accounts: senders subscribed to a feedback loop (FBL) receive reports containing information on the sender's emails that a recipient marked as spam.
Most of the largest email account providers (internet services like Comcast or webmail services like Yahoo! Mail) offer feedback loops, though they require senders to fulfill certain criteria before being granted access.
ISP. Internet Service Provider.
ISPs provide their customers (individuals and organizations) with internet connections. Large providers of webmail email accounts (like Gmail) are also commonly referred to as ISPs.
ISPs play a major role in email marketing through their control of the transfer of mails to their customers' email accounts. They use various tools to sort the flow of incoming messages and identify unwanted email.
Unwanted email is normally deleted, rerouted to a junk file or folder, or delivered to the recipient's inbox with some kind of "this is spam" warning attached.
Sender reputation. A reputation score assigned to an individual sender by organizations managing incoming email.
The higher the score, the more likely they will deliver that sender's emails to the end user.
A reputation score is calculated using various criteria and measures, such as the number of spam complaints generated by a sender and the quality of the infrastructure used to distribute the sender's emails.
Read more about sender reputation.
Spam complaints. Manual reports of spam from email users.
Webmail services, for example, provide their customers with a "report spam" button. Email recipients can then use this button to mark a message as spam, even though the service
itself delivered the message to the recipient's inbox as a legitimate email.
Using the button generates a spam complaint which is forwarded to the webmail service, providing them with useful intelligence for refining their anti-spam processes.
The number of spam complaints a sender gets is an important factor in deciding how email services handle future emails from that sender. For example, excessive spam complaints can cause a sender to be added to a blacklist (or removed from a whitelist).
Spam filter. Any technology or process used to examine incoming email with the aim of distinguishing between legitimate messages and spam.
Spam filters may be applied at various stages of the email transfer. Large organizations, for example, use spam filters to sort email before it reaches the intended recipient.
Messages identified as legitimate email are forwarded to the recipient's email account. Messages identified as spam may be "filtered out" (i.e. deleted) or forwarded to the spam/junk folder of the recipient's account.
Spam trap. A spam trap is an email address created and used by anti-spam organizations, ISPs and others to identify spammers.
A typical spam trap is an email address which is never used for correspondence or for signing up to mailing lists, but which is posted on a webpage somewhere. By definition, any email sent to that address is unsolicited and therefore spam.
Read more about spam traps.
Webmail service. Any email account provider that allows its users to access their inbox on the web, simply by logging on to a website.
The three most popular webmail services are Yahoo! Mail, Gmail (Google) and Windows Live Hotmail, who together provide email accounts to hundreds of millions of users.Webmail services are important to email marketers because:
- most email address lists include a large number of webmail accounts
- each webmail service has its own interpretation of how an email should be displayed and whether to display or block certain types of content within emails (particularly images)
- each service has its own tools and technologies in place to filter and manage incoming email. Understanding these tools and technologies is important for ensuring your email is delivered to recipients' inboxes.
Whitelist. A list of trusted email senders who are known to meet appropriate mailing standards.
Organizations give priority treatment to emails arriving from whitelisted senders. They may, for example, deliver them straight to the recipient's inbox without subjecting them to any spam filters .
Organizations managing incoming email may use their own whitelist(s) or refer to a whitelist managed by a third party. While some whitelists are compiled based on observed sending behavior, most require senders to formally apply for a listing.
Read more about whitelists .