Email Warm-upEmail warm-up glossary
Twenty terms you will meet when fixing deliverability, each defined in two or three sentences with the number that matters. Linked from every guide on this site.
Email warm-up
The practice of sending a slowly growing number of ordinary, two-way emails from a new or idle mailbox so that providers see opens, replies and spam rescues before real outreach starts. Typically 14 days for an existing domain, 3–4 weeks for a new one.
Sender reputation
A score each receiving provider keeps for a sending mailbox, domain and IP, built from history: volume, engagement, complaints, bounces and whether mail is pulled out of Spam. It is the main reason two identical emails land in different folders.
Domain reputation
The part of sender reputation tied to the sending domain rather than the mailbox or IP. Shared by every mailbox on the domain, which is why one abusive mailbox hurts all of them.
IP reputation
Reputation of the sending server's IP address. On Gmail, Workspace, Zoho and similar shared infrastructure the provider manages it; on Amazon SES, SendGrid or Mailgun with a dedicated IP it is yours to warm.
Warm-up pool
The set of mailboxes that exchange warm-up emails with each other. In a shared network they belong to many customers; in a private pool they all belong to one account.
Private pool
A warm-up pool made only of one account's own mailboxes. Nobody else's inbox receives your addresses, and no stranger's bad behaviour touches your reputation.
Spam rescue
Moving a warm-up email that landed in the Spam folder back to the inbox and marking it read. Receivers treat this as a human correction and it is the strongest positive signal in warm-up.
Spam rate
In warm-up, the share of a sender's warm-up emails that receiving mailboxes found in Spam over a period, typically 7 days. Different from Google's spam complaint rate, which counts recipients pressing Report spam.
Spam complaint rate
Recipients who mark your mail as spam divided by mail delivered to the inbox. Google asks bulk senders to stay under 0.1% and never above 0.3%.
Ramp
The schedule by which daily warm-up volume grows, for example 3 emails on day one, plus 2 a day, capped at 30. Ramping too fast is the most common cause of a new mailbox being throttled.
Ready for outbound
The point at which a warmed mailbox can carry real outreach. A practical gate: 14 days of warm-up, a 7-day spam rate at or under 3%, and at least 30 warm-up emails received.
SPF
Sender Policy Framework. A DNS TXT record on the domain listing the servers allowed to send for it, for example v=spf1 include:_spf.google.com ~all. Limited to 10 DNS lookups.
DKIM
DomainKeys Identified Mail. A cryptographic signature added to each message and verified against a public key published at selector._domainkey.domain. Must be enabled in the provider's admin, not just published.
DMARC
A DNS policy at _dmarc.domain telling receivers what to do when SPF and DKIM fail or do not align with the From domain: p=none (monitor), p=quarantine (spam), p=reject. It also sends you reports.
Alignment
The DMARC requirement that the domain authenticated by SPF or DKIM matches the From domain. Relaxed alignment accepts subdomains; strict requires an exact match.
Inbox placement
Where a delivered email lands: inbox, promotions, or spam. Different from delivery, which only means the receiving server accepted the message.
Seed list
A set of test mailboxes across providers used to measure where a message lands. Warm-up services that use their own pool measure placement in real inboxes instead.
Bulk sender rules
Requirements Google and Yahoo apply to domains sending roughly 5,000 or more messages a day to their users: SPF and DKIM, DMARC, aligned From domain, one-click unsubscribe for marketing mail, and a low complaint rate.
Secondary domain
A domain registered only for outreach so the main company domain's reputation is never at risk. It needs its own records, mailboxes and 3–4 weeks of warm-up.
Block list (blacklist)
A DNS-based list of IPs or domains reported for spam, queried by receiving servers. A listing explains spam placement that warm-up cannot fix until the listing is removed.
Put the terms to work
Connect two mailboxes and watch the spam rate, rescues and ramp on a real dashboard. Free, private pool.