Clear, plain-English definitions of the email marketing terms that matter — from open rate to double opt-in. New terms are added regularly.
- Bounce rate — the percentage of sent emails that could not be delivered.
- Click-through rate (CTR) — the percentage of delivered emails in which the recipient clicked a link.
- Click-to-open rate (CTOR) — clicks as a share of opens — how compelling the email is once opened.
- Conversion rate (email) — the percentage of recipients who completed a desired action after clicking.
- Double opt-in — subscribers confirm their address before joining your list.
- Hard bounce — a permanent delivery failure — remove these immediately.
- List segmentation — dividing subscribers into groups for more relevant sends.
- Open rate — the percentage of delivered emails that were opened.
- Soft bounce — a temporary delivery failure that may retry.
- Unsubscribe rate — the percentage of recipients who opted out after a send.
Deliverability & authentication
- SPF — the DNS record listing which servers may send email for your domain.
- DKIM — a cryptographic signature proving an email really came from your domain.
- DMARC — the policy telling receivers what to do with mail that fails SPF and DKIM.
- Sender score — a 0–100 reputation rating for a sending IP address.
- Spam trap — a hidden address used to catch senders with poor list hygiene.
- Greylisting — temporarily rejecting unknown senders so only legitimate ones retry.
- Allowlist — approved senders that bypass spam filtering.
- Feedback loop (FBL) — a provider alert when a recipient marks your email as spam.
- Sender reputation — the overall trust providers assign to your domain and IP.
- Dedicated IP — an IP used by one sender only, with its own reputation.
Automation
- Drip campaign — a series of emails sent automatically on a schedule or by trigger.
- Trigger — the event or condition that starts an automated email or workflow.
- Workflow — the branching sequence of emails, waits, and conditions after a trigger.
- Lead scoring — points assigned to contacts to prioritize the most sales-ready.
- Autoresponder — an email sent automatically in response to a single event.
- Customer journey — the full path a contact takes from first touch to purchase and beyond.
- Suppression list — addresses your platform will never send to, protecting deliverability.
Analytics & paid
- Attribution — assigning conversion credit across the touchpoints that led to a sale.
- Cohort — a group of contacts sharing a signup window, tracked over time.
- Deliverability rate — the share of sent emails that actually reach the inbox.
- ROAS — revenue earned per unit of ad spend, as a ratio.
- Customer acquisition cost (CAC) — total spend to win one new customer.
- Customer lifetime value (LTV) — the total profit expected from a customer over the relationship.
- Engagement rate — a composite measure of how actively subscribers interact.
- Conversion funnel — the delivered-to-converted sequence, showing where people drop off.
New to email marketing? Start with our complete email marketing guide.