Cold email glossary

Plain definitions for the terms that come up around cold email and deliverability — used throughout the blog and docs.

Cold email

An email sent to someone you have no prior relationship with, typically to introduce a product or service. Distinct from spam in that it should be targeted, personalized, and easy to opt out of.

SPF (Sender Policy Framework)

A DNS record listing which mail servers are allowed to send email on behalf of your domain. Receiving servers check it to help decide whether a message is legitimate.

DKIM (DomainKeys Identified Mail)

A cryptographic signature added to outgoing email, verified against a public key in your DNS, that proves the message wasn't altered in transit and genuinely came from your domain.

DMARC

A DNS policy that tells receiving servers what to do with mail that fails SPF or DKIM checks — quarantine it, reject it, or let it through — and where to send reports about it.

Deliverability

The likelihood that an email actually reaches the recipient's inbox rather than being filtered to spam or blocked outright. Driven by sender reputation, authentication (SPF/DKIM/DMARC), content, and sending patterns.

Sender reputation

A score mailbox providers assign to a sending domain or IP based on its history — bounce rates, spam complaints, engagement — that influences whether future mail lands in the inbox or spam folder.

Mailbox warmup

Gradually increasing the volume and pace of emails sent from a new or dormant mailbox over time, instead of sending at full volume immediately, to build sender reputation without triggering spam filters.

Bounce rate

The percentage of sent emails that fail to deliver. A hard bounce means the address is invalid; a soft bounce is usually temporary (full inbox, server issue). High bounce rates damage sender reputation.

Spam trap

An email address, often abandoned or never used, set up specifically to catch senders using outdated or unverified lists. Emailing one signals poor list hygiene and can trigger blocklisting.

Open rate

The percentage of delivered emails that were opened by the recipient. Increasingly unreliable as a metric since privacy features in mail clients can trigger false opens.

Reply rate

The percentage of sent emails that received any reply, positive or negative. A more reliable indicator of outreach quality than open rate.

ICP (Ideal Customer Profile)

A description of the type of company or person most likely to become a good customer — industry, size, role, and other qualifying traits used to target outreach.

Email sequence

A series of emails sent to a lead over time — typically a first-touch message followed by one or more scheduled follow-ups if there's no reply.

Personalization

Tailoring an email's content to a specific recipient using real details about them or their company, rather than sending an identical template to everyone.

GDPR

The EU's General Data Protection Regulation, governing how personal data (including business contact details) can be collected, used, and stored. Applies to cold email sent to contacts in the EU regardless of where the sender is based.

CAN-SPAM Act

US law setting requirements for commercial email: accurate sender information, no deceptive subject lines, a working opt-out mechanism, and honoring opt-outs promptly.

Lead

A person or company identified as a potential customer, typically with enough contact information (like a verified email) to be reached directly.

Prospecting

The process of identifying and researching potential customers before reaching out to them.