The cold email glossary

A/B testing in cold email

A/B testing in cold email is the practice of sending two message variants to randomly split, comparable segments of a list and comparing results to decide which version to scale. Variants typically differ in one element, such as the offer, the opener, or the subject line.

B2B lead generation

B2B lead generation is the process of identifying, attracting, and qualifying potential business customers for a company's product or service. It spans inbound channels like content and search, and outbound channels like cold email and calling.

BIMI (Brand Indicators for Message Identification)

BIMI (Brand Indicators for Message Identification) is an email standard that displays a verified brand logo next to authenticated messages in supporting inboxes. It only activates for domains with a DMARC policy at enforcement, meaning quarantine or reject.

Bounce rate

Bounce rate is the percentage of sent emails that are rejected and returned undelivered by the receiving server. It is calculated by dividing bounced messages by total messages sent, and it is a primary signal of list quality.

CAN-SPAM Act

The CAN-SPAM Act is the United States federal law that sets the rules for commercial email. It does not require prior consent to send, but it requires truthful headers, a non-deceptive subject line, a valid physical postal address, and a working way to opt out that is honored within 10 business days.

Catch-all email

A catch-all email is a domain configuration where the mail server accepts messages addressed to any mailbox at the domain, whether or not that mailbox exists. Because the server accepts everything, verification tools cannot confirm whether a specific address is real.

Cold email personalization

Cold email personalization is the practice of tailoring an outreach message to a specific recipient using details about their role, company, or recent activity. It ranges from inserting merge fields like a first name to writing custom opening lines based on individual research.

Cold email sequence

A cold email sequence is a planned series of emails sent to the same prospect over a set period, where each message goes out only if the prospect has not replied to the previous one. Sequences typically run three to five emails over two to four weeks.

Dedicated sending domain

A dedicated sending domain is a separate domain used exclusively for outbound email, keeping cold outreach isolated from a company's primary domain. If its reputation is damaged, email on the main domain is unaffected.

DKIM (DomainKeys Identified Mail)

DKIM (DomainKeys Identified Mail) is an email authentication method that adds a cryptographic signature to each outgoing message. Receiving servers verify the signature against a public key published in the sender's DNS, confirming the message came from that domain and was not altered in transit.

DMARC

DMARC (Domain-based Message Authentication, Reporting, and Conformance) is an email authentication protocol that tells receiving servers how to handle messages that fail SPF or DKIM alignment checks. It also sends the domain owner reports showing who is sending mail using its domain.

Domain reputation

Domain reputation is the trust assessment a mailbox provider assigns to a sending domain based on its history of authentication, spam complaints, bounces, spam trap hits, and recipient engagement. It is a major input into whether mail from that domain reaches the inbox, lands in spam, or is rejected.

Email blocklist

An email blocklist is a published database of IP addresses or domains that have been identified as sources of spam or abuse. Mail servers and spam filters consult blocklists in real time to decide whether to reject, filter, or accept incoming mail.

Email deliverability

Email deliverability is the ability of your emails to reach the recipient's inbox rather than being filtered to spam or rejected. It is determined mainly by sender reputation, authentication, and engagement signals.

Email service provider (ESP)

An email service provider (ESP) is a platform that sends email on a business's behalf, most commonly a marketing platform built for opted-in subscriber lists. The term is also used loosely for inbox providers like Gmail and for any tool that sends email.

Email spoofing

Email spoofing is forging the From address of an email so it appears to come from a domain the sender does not control. SPF, DKIM, and DMARC are the authentication standards built to detect and block it.

Email throttling

Email throttling is the practice of limiting how many emails are sent or accepted over a given period. Receiving servers throttle inbound mail from senders they do not fully trust, and careful senders throttle their own outbound volume to protect reputation.

Email verification

Email verification is the process of checking whether an email address is valid and able to receive mail before you send to it. It removes invalid, risky, and undeliverable addresses from a list so that far fewer sends bounce.

Email warmup

Email warmup is the process of gradually increasing sending volume from a new domain or mailbox so mailbox providers learn to trust it. It builds the sender reputation required to land in the inbox before real outreach begins.

Follow-up email

A follow-up email is any message sent to a prospect after the initial cold email, triggered only when the prospect has not replied. Effective follow-ups add new information or a new angle rather than repeating the original ask.

GDPR and cold email

GDPR does not ban B2B cold email, but it regulates the personal data behind it, including a prospect's name and work email address. Most B2B senders rely on legitimate interest as their lawful basis, which requires a documented balancing test, clear disclosures, and an easy way to object.

Google Postmaster Tools

Google Postmaster Tools is a free dashboard from Google that shows how Gmail treats mail from your domain, including spam complaint rate, domain and IP reputation, and authentication results. It is one of the few first-party views into how a major mailbox provider scores a sender.

Ideal customer profile (ICP)

An ideal customer profile (ICP) is a description of the type of company that gets the most value from your product and is most likely to buy, stay, and expand. It usually combines firmographic traits like industry, headcount, and business model with situational signals like the tools a company runs or the problems it is hiring to solve.

Inbox placement

Inbox placement is the rate at which accepted emails land in the recipient's primary inbox rather than the spam folder or a secondary tab. It measures where messages end up after delivery, not whether the receiving server accepted them.

Intent data

Intent data is behavioral information suggesting that a company is actively researching a problem or product category, gathered from sources like website visits, content consumption, review-site activity, and search behavior. Sales teams use it to decide which prospects to contact first and when.

List hygiene

List hygiene is the ongoing practice of keeping an email list accurate, deliverable, and relevant by removing invalid, stale, and risky addresses. It protects sender reputation by keeping bounce and complaint rates low.

MX record

An MX (mail exchange) record is a DNS record that tells other mail servers where to deliver email addressed to a domain. Without a valid MX record, a domain cannot reliably receive mail.

Open rate

Open rate is the percentage of delivered emails recorded as opened, measured by an invisible tracking pixel that loads when the message is displayed. Since Apple Mail Privacy Protection began preloading remote images in 2021, the metric can significantly overstate how many humans actually read a message.

Outbound sales

Outbound sales is the practice of proactively contacting potential customers who have not expressed interest, typically through cold email, cold calling, and LinkedIn outreach. The seller chooses the accounts and starts the conversation rather than waiting for inbound leads.

Positive reply rate

Positive reply rate is the percentage of delivered cold emails that receive a reply expressing interest, such as a request for more detail, pricing, or a meeting. It refines raw reply rate by excluding negative and neutral responses.

Reply rate

Reply rate is the percentage of delivered cold emails that receive a response, calculated as unique replies divided by delivered messages. It is the primary engagement metric in cold email because it measures real human action and cannot be inflated by tracking artifacts.

SDR (Sales Development Representative)

An SDR (sales development representative) is a salesperson who works the top of the funnel: finding prospects, starting conversations through cold email, calls, and LinkedIn, and booking qualified meetings for account executives to close.

Sender reputation

Sender reputation is the trust assessment mailbox providers assign to a sending domain and IP address based on its history of spam complaints, bounces, engagement, and authentication. It is the main input providers use to decide whether mail reaches the inbox.

Spam complaint rate

Spam complaint rate is the percentage of delivered emails that recipients mark as spam or junk. Google and Yahoo's published bulk sender guidance asks senders to keep spam rates below 0.3 percent, and mailbox providers treat the metric as a core reputation signal.

Spam trap

A spam trap is an email address operated by mailbox providers, blocklist operators, or anti-spam organizations to identify senders with poor list practices. The address never opts in to anything, so any mail it receives marks the sender as careless or abusive.

SPF (Sender Policy Framework)

SPF (Sender Policy Framework) is an email authentication standard that lets a domain owner publish a DNS record listing the mail servers authorized to send email on its behalf. Receiving servers check this record to decide whether an incoming message came from an approved source.

Spintax

Spintax, short for spinning syntax, is a templating format that defines interchangeable text variants inside curly braces, such as {Hi|Hello|Hey} {{firstName}}, so each generated message uses a randomly chosen variation. In cold email it is used to vary copy across sends so no two messages are identical.

Total addressable market (TAM)

Total addressable market (TAM) is the total revenue opportunity available if a product reached every possible customer in its market. In outbound sales, the term is also used more concretely to mean the complete list of companies that fit your ideal customer profile.

Trigger event

A trigger event is a public, observable change at a company, such as a funding round, a leadership hire, an office opening, or a relevant job posting, that makes the company more likely to buy a particular product right now. Trigger events add timing to targeting: the ideal customer profile says who to contact, and triggers say when.

Unsubscribe compliance

Unsubscribe compliance means giving every recipient of commercial email a clear way to opt out and honoring the request within the required window. In the US, CAN-SPAM allows at most 10 business days, and Google and Yahoo's bulk sender guidance requires one-click unsubscribe honored within two days.