The cold email glossary
Every infrastructure, deliverability, and outreach term — defined in plain English, with concrete examples.
An Azure tenant is a dedicated Microsoft cloud instance that can host up to 100 mailboxes per domain at a fraction of per-mailbox cost.
API provisioning is creating and configuring mailboxes programmatically rather than through a UI.
A recurring affiliate program pays a percentage of every invoice for as long as the referred customer remains, not just the first payment.
A blacklist (RBL) is a list of IPs or domains known to send spam, used by mail receivers to block or filter incoming mail.
Bounce rate is the percentage of sent emails that fail to deliver, either permanently (hard) or temporarily (soft).
Blast radius is the number of mailboxes or domains affected when one piece of infrastructure is suspended, blacklisted, or burned.
A burned mailbox or domain has accumulated enough negative reputation that it can no longer reliably reach the inbox.
Bulk sender requirements are the 2024 rules from Google and Yahoo mandating SPF, DKIM, DMARC, one-click unsubscribe, and spam complaint rates under 0.3% for senders above 5,000/day.
A CNAME is a DNS alias that points one hostname to another, commonly used for custom tracking domains.
A catch-all domain accepts every email regardless of whether the address exists, making verification unreliable.
Click tracking rewrites outbound links through a tracking domain to measure recipient interaction.
A custom tracking domain is a CNAME you control (like track.yourdomain.com) used for link tracking instead of a shared platform domain.
Cold email infrastructure is the stack of domains, mailboxes, authentication, warmup, and monitoring that powers sending — separate from the sequencer that schedules it.
CAN-SPAM is the US federal law governing commercial email, requiring honest headers, clear identification, a physical address, and a working unsubscribe mechanism.
DKIM (DomainKeys Identified Mail) is a cryptographic signature added to outgoing email that proves the message wasn't altered in transit.
DMARC is a DNS policy that tells receiving servers what to do when SPF or DKIM checks fail for your domain.
DNS propagation is the time it takes for a DNS change to be visible across global resolvers, typically 5 minutes to 48 hours depending on TTL.
Deliverability is the discipline of getting email reliably into the primary inbox, combining authentication, reputation, content, and engagement.
Domain reputation is the deliverability score attached to your sending domain, independent of IP, that follows you across providers.
A dedicated IP is a sending IP address used exclusively by one sender, so reputation depends only on their own behavior.
Domain isolation is the practice of giving each sending domain its own separate workspace or tenant so reputation damage on one domain can never spread to others.
DFY (done-for-you) infrastructure is mailbox setup where the provider owns the domains and accounts, charging a premium for the convenience.
Email verification is the process of checking whether an address is syntactically valid and deliverable before sending.
ESP (Email Service Provider) is the company hosting your mailbox — Google, Microsoft, Amazon SES, your own SMTP server.
ESP matching is the practice of sending from the same ESP your recipients use, since same-ESP delivery typically sees better placement.
Google Workspace is Google's business email platform built on Gmail infrastructure, the default choice for high-deliverability cold email.
GDPR is the EU data protection law that restricts processing personal data of EU residents, including business email addresses in cold outreach.
Inbox placement is the percentage of your sent emails that actually reach the recipient's primary inbox rather than spam or promotions.
IP reputation is the deliverability score attached to the sending IP address used to deliver your mail.
IMAP is the standard protocol for reading mail from a server, used by sequencers to fetch replies.
An MX record is a DNS entry that tells the internet which mail server receives email for your domain.
Mailbox rotation distributes sending across many mailboxes to stay within per-account daily limits.
Mailbox replacement is the process of retiring a burned mailbox and provisioning a fresh one to take its place in your sending rotation.
Microsoft 365 is Microsoft's business email platform built on Exchange Online, required for reaching Outlook-heavy audiences.
An MCP server exposes your infrastructure as tools for AI assistants over the Model Context Protocol, so agents can provision and manage mailboxes autonomously.
Open rate is the percentage of recipients who opened your email, measured via tracking pixel.
OAuth and app passwords are two ways for a sequencer to authenticate to your mailbox — OAuth uses scoped tokens, app passwords use fixed credentials.
One-click unsubscribe is an email header (List-Unsubscribe-Post) that lets recipients unsubscribe with a single click, required by Google/Yahoo for bulk senders.
A pre-warmed mailbox is an email account with existing sending history and established reputation, allowing campaigns to start immediately instead of waiting through a 14–21 day warmup.
Positive reply rate is the percentage of replies that express interest, separating genuine pipeline from objections and unsubscribes.
Personalization tokens insert per-recipient values like {{first_name}} or {{company}} into emails at send time.
SPF (Sender Policy Framework) is a DNS TXT record that lists which mail servers are authorized to send email on behalf of your domain.
Sender reputation is a mailbox provider's score of how trustworthy your sending domain and IP are, based on engagement, bounces, and complaints.
A shared IP is a sending address used by multiple senders simultaneously, pooling reputation and risk.
A spam trap is an email address used by anti-spam organizations to identify senders with poor list hygiene.
A soft bounce is a temporary delivery failure caused by full inboxes, server outages, or greylisting.
A sequencer is the outreach tool that schedules, personalizes, and sends multi-step email campaigns across your mailboxes.
SMTP is the standard protocol for sending mail between servers, used by sequencers to deliver outbound email.
Spintax is markup syntax {like|such as|including} this that lets sequencers randomly substitute phrases to vary email content.
A suppression list is the master record of addresses that must never be contacted again — unsubscribes, complaints, bounces.
Self-healing inboxes are mailboxes that detect their own degradation and automatically trigger replacement before deliverability drops.
Warmup is the gradual ramp-up of sending volume on a new mailbox, paired with positive engagement signals, that builds sender reputation before real campaigns begin.
Workspace isolation puts each domain or each client into its own provider workspace/tenant to prevent cross-contamination of reputation or bans.
Whitelabel is reselling infrastructure under your own brand, so clients see your dashboard and pricing instead of the underlying provider.