Email Deliverability Terms You Need to Know

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Effective communication with customers is the heart beat of most companies. Today, email has emerged and still reigns as the most common and effective form of direct customer communication. However, emailing customers has become a complicated battlefield filled with spam filters, blacklists, and fickle consumers. To navigate this effectively, email deliverability testing has become a billion dollar industry. Like all new industries, it has its own terms and definitions. We’re going to walk through the most common email deliverability terms and definitions to keep you current and moving forward onto your next marketing campaign.

  • Deliverability

    The ability or lack thereof to deliver email to a specific inbox.

  • Spam

    Email sent to a recipient who didn’t give permission to be emailed.

  • Spam Report

    Report of an email being market as spam, whether it’s spam or not


    Originally an acronym for a federal act which controlled non-solicited email, and is now also used as a term for bulk emails campaigns

  • Spam Trap

    Email that is recognized by a server as going to a dead address and because of this is automatically reported as spam

  • Email Blacklists

    Email blacklists are lists created to identify “known” spammer IPs and domains. It is common practice for ISPs (internet service providers) to blacklist the IPs and domains of suspected spammers.

  • Email Blocking

    Email blocking occurs when the receiving email server blocks incoming mail. Mail services (Yahoo!, Gmail, etc) will often block email from reaching the inbox when the sender is a suspected spammer.

  • Hard Bounce or Soft Bounce

    A hard bounce is the permanent delivery failure of an email for a number of reasons, most commonly a non-existent email address. Sometimes delivery failure isn’t permanent and is caused by a temporary issue, which is called a soft bounce.

  • Acceptance Rate

    The percentage of emails in a campaign that pass mail server filters without being blocked or marked as spam.

  • Single Opt In

    An individual adding their email address to a mailing list usually by filling out a web form without a subsequent confirmation step

  • Double Opt In

    Same as a Single Opt In but with the addition of a confirmation step

  • Open Rate

    The percentage of opened emails in an email campaign (this should not be confused with deliverability)

Have any more email deliverability terms you want to share? Let us know!



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