Sending two versions of an email to comparable prospects to see which gets more replies.
Bounce rate
The share of sent emails that could not be delivered. Hard bounces come from invalid addresses; soft bounces from temporary problems such as a full mailbox.
Catch-all domain
A mail domain that accepts mail for any address, so a verifier cannot confirm whether a specific mailbox exists.
Cold email
An unsolicited email to a business contact who has had no prior contact with the sender.
Decision maker
The person at a target company who can approve a purchase, such as a founder, department head or budget owner.
DKIM
DomainKeys Identified Mail. A signature added to outgoing mail that lets the receiving server check the message was sent by the domain and not altered.
DMARC
A DNS policy that tells receiving servers what to do with mail that fails SPF or DKIM checks, and where to send reports.
Email verification
Checking whether an address exists and can receive mail before sending to it, to keep bounce rates low.
Follow-up
A later email in a sequence sent to a prospect who has not replied.
ICP
Ideal customer profile. The description of the companies most likely to buy: industry, size, location, technology and similar traits.
Inbox rotation
Spreading outreach across several sending mailboxes so no single inbox exceeds safe daily volume.
Lead list
The set of contacts selected for a campaign, usually with name, title, company and email.
Open rate
The share of delivered emails that were opened. Privacy features in mail clients make it an unreliable number.
Opt-out
A recipient's request to receive no further emails. Senders must stop contacting that address.
Personalization
Details in an email that refer to the specific recipient or company, such as their product, role or recent news.
Reply rate
The share of prospects who replied to a campaign. The main success measure for cold email.
Sender reputation
The trust score mailbox providers assign to a sending domain or IP, based on bounces, complaints and engagement.
Sequence
A planned series of emails sent to a prospect over days or weeks, stopping when they reply.
Spam complaint
A recipient marking an email as spam. High complaint rates damage sender reputation.
SPF
Sender Policy Framework. A DNS record listing the servers allowed to send mail for a domain.
Warm-up
Gradually raising a new mailbox's sending volume over weeks so mailbox providers learn to trust it.