Email tracking and deliverability glossary
Definitions of the technical, regulatory, and metric terms that show up in B2B email tracking and deliverability decisions. Each entry includes a quick definition, detailed explanation, related terms, and FAQs.
Apple Mail Privacy Protection
Apple MPP, Mail Privacy Protection, MPP
Apple Mail Privacy Protection (MPP) is a privacy feature that launched with iOS 15 in September 2021.
Email Tracking Pixel
Tracking pixel, Web beacon, 1x1 pixel
An email tracking pixel is a 1x1 transparent image embedded in an email that loads from a tracker server when the recipient's mail client renders the message.
Email Open Rate
Open rate, Email opens, Open percentage
Email open rate is the percentage of email recipients whose mail client loaded the tracking pixel embedded in the message.
Gmail Image Proxy
googleusercontent.com, Gmail image cache
Gmail's image proxy is the system Google uses to route every embedded image in incoming Gmail messages through googleusercontent.
Email Deliverability
Deliverability, Inbox placement, Email delivery rate
Email deliverability is the rate at which sent emails reach the recipient's inbox rather than spam folder or being blocked entirely.
SPF, DKIM, and DMARC
Email authentication, SPF record, DKIM signature
SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting & Conformance) are the three email authentication standards published as DNS records on the sender domain.
Sender Reputation
Domain reputation, IP reputation, Sender score
Sender reputation is the score that mail providers (Gmail, Microsoft 365, Yahoo) assign to your sending domain and IP based on historical behaviour: bounce rate, spam-complaint rate, recipient engagement (opens, clicks, replies, deletes-without-reading), and consistency over time.
Email Warm-up
Sender warm-up, Inbox warm-up, Domain warm-up
Email warm-up is the practice of gradually ramping email volume from a new sending domain or IP to build positive sender reputation with mail providers.
Cold Email
Cold outreach, Outbound email
Cold email is outbound email sent to a recipient who has not opted in to receive email from the sender.
Email Bounce Rate
Bounce rate, Hard bounce, Soft bounce
Email bounce rate is the percentage of sent emails that fail to deliver to the recipient's mailbox.