Delivery
Email delivery refers to the successful transmission of an email from the sender’s mail server to the recipient’s mail server. An email is considered delivered when it has been accepted by the receiving server.
This is distinct from deliverability, which concerns what happens next: whether the email lands in the inbox, the spam folder, or somewhere else entirely. Delivery is the binary first step. The email either arrived at the destination server or it did not. If it did not, it bounced.
A high delivery rate is a prerequisite for everything else in email marketing. You cannot measure opens, clicks, or conversions on emails that never arrived. Hard bounces, which indicate a permanent delivery failure, such as a nonexistent address, directly harm your sender’s reputation if left unaddressed. Soft bounces, which indicate a temporary failure such as a full inbox, are less serious but worth monitoring for patterns.
For B2B marketers, maintaining strong delivery rates means keeping your contact list clean, promptly removing hard bounces, and sending from authenticated domains. The infrastructure basics, SPF, DKIM, and DMARC records, are what prove to receiving servers that you are a legitimate sender. Get those right, and delivery takes care of itself. Neglect them, and even well-crafted emails may never reach a mail server at all.
What is the difference between email delivery and email deliverability?
Delivery refers to whether an email reached the recipient’s mail server. It is a pass-or-fail measure. Deliverability refers to where an email ends up after delivery, specifically whether it lands in the inbox or the spam folder. You can have a high delivery rate but poor deliverability if your emails are consistently being filtered into spam.
What causes an email not to be delivered?
The most common causes of delivery failure are invalid or non-existent email addresses (hard bounces), a full or temporarily unavailable recipient mailbox (soft bounces), the sending domain or IP being on a blacklist, failed authentication checks such as SPF or DKIM, and the recipient’s server actively rejecting emails from your domain or IP. Each of these has a different remedy.
How is the delivery rate calculated?
Delivery rate is calculated by dividing the number of emails successfully accepted by the receiving server by the total number of emails sent, then multiplying by 100. A delivery rate of 95% or above is generally considered healthy. Anything lower warrants investigation into bounce types, list quality, and sender authentication setup.