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Cold email glossary

Plain-English definitions of the words you'll meet when you set up cold email.

What is cold email infrastructure?

Cold email infrastructure is the set of domains, mailboxes, DNS authentication records, warmup and sending software used to run outbound email separately from a company's main domain. It typically means several lookalike domains with 2–3 mailboxes each, SPF, DKIM and DMARC on every domain, a few weeks of gradual warmup, and a sequencer that spreads sends across all mailboxes.

3 min read · updated 2026-10-17

Sending domain: A separate domain (like getacme.com) used only for cold email, so your main domain stays safe.
Mailbox: One email account with its own address and password, for example ana@getacme.com.
SPF: A DNS record that lists which servers may send email for your domain.
DKIM: A digital signature on each email that proves it really came from your domain.
DMARC: A DNS record telling inbox providers what to do with mail that fails SPF or DKIM.
Warm-up: Slowly increasing how many emails a new mailbox sends, so providers learn to trust it.
Sequencer: A tool such as Instantly or Smartlead that sends a series of follow-up emails automatically.
Inbox placement: Whether your email lands in the inbox, the spam folder or the promotions tab.
Blocklist: A public list of domains or servers known for spam; being on one hurts delivery.
Bounce: An email that couldn't be delivered, for example because the address doesn't exist.
Lookalike domain: A domain close to your brand name, such as tryacme.com for acme.com, so prospects still recognise you.
Catch-all: A domain that accepts mail for any address, so a verifier can't tell whether one mailbox exists.

Last updated 1 November 2026 · by Venu Gopal Reddy Muvva, founder