Cold email deliverability glossary

In DMARC, alignment means the domain in the visible From address matches the domain that SPF or DKIM authenticated, either exactly (strict) or at the organizational-domain level (relaxed). A message passes DMARC when at least one of SPF or DKIM passes and aligns with the From domain (RFC 9989).

See also DMARC, SPF, DKIM.

A list of IP addresses or domains that mailbox providers and filtering services consult when deciding whether to reject or filter mail. Listings usually follow spam-trap hits or complaints, and most blocklists publish a delisting process.

See also Spam trap, Sender reputation.

The share of sent messages that came back as undeliverable. A rising bounce rate usually points to an old or unverified list, and it harms sender reputation.

See also Hard bounce, Soft bounce, List hygiene.

Google's term for a sender that sends close to 5,000 or more messages a day to personal Gmail accounts. Bulk senders must meet extra requirements, including SPF, DKIM and DMARC, one-click unsubscribe for marketing and subscribed messages, and a low spam rate (Google's email sender guidelines). Yahoo and Microsoft (for Outlook.com) publish similar requirements for high-volume senders.

See also One-click unsubscribe, Spam complaint rate, DMARC.

A domain set up to accept mail for any address, whether or not a mailbox with that name exists. Email verification cannot confirm individual addresses on a catch-all domain, so they are usually reported as risky or unknown rather than valid.

See also List hygiene, Bounce rate.

A tab in a mailbox, such as Gmail's Promotions or Updates tab, that sorts mail out of the main inbox view. A message in a category tab was delivered and not treated as spam, but it is less likely to be seen than one in the primary inbox.

See also Inbox placement, Spam folder.

A DNS record that makes one hostname an alias of another. A custom tracking domain is usually a CNAME record that points a subdomain of your sending domain at your sequencer's tracking host.

See also DNS, Tracking domain.

Email sent to someone who has no prior relationship with the sender, usually one-to-one business outreach. Because the recipient did not ask for it, cold email depends on careful targeting, authenticated domains and modest volumes per inbox to stay out of spam.

See also Sequencer, Deliverability, Sending limit.

How reliably your email reaches the recipient's inbox, rather than being rejected or landing in spam or a category tab. It depends on authentication, sender reputation, list quality, content and sending patterns.

See also Inbox placement, Sender reputation.

DomainKeys Identified Mail: a cryptographic signature added to each message and checked against a public key the signing domain publishes in DNS. It lets the receiver confirm that the domain took responsibility for the message and that the signed parts were not changed in transit (RFC 6376).

See also SPF, DMARC, Alignment, TXT record.

Domain-based Message Authentication, Reporting and Conformance: a DNS TXT record at _dmarc on your domain that tells receivers what to do with mail that fails aligned SPF and DKIM (none, quarantine or reject) and where to send reports (RFC 9989). Google requires bulk senders to publish one.

See also SPF, DKIM, Alignment, Bulk sender.

The Domain Name System: the public directory that maps domain names to the records that mail and web servers rely on. Mail routing (MX), email authentication (SPF, DKIM and DMARC) and tracking domains (CNAME) all live in a domain's DNS.

See also MX record, TXT record, CNAME record, PTR record.

The trust a mailbox provider gives your sending domain, built from how recipients have responded to mail from it over time. It follows the domain across IP addresses and sending tools, so a new domain starts with little history and a damaged one is slow to recover.

See also Sender reputation, IP reputation, Warm-up.

A program in which a mailbox provider tells the sender when recipients mark its messages as spam. Some providers send a report for each complaint, while Gmail shows aggregate complaint data in Postmaster Tools for senders that add a Feedback-ID header.

See also Spam complaint rate, Postmaster Tools.

Google's paid suite for businesses, which provides Gmail mailboxes on a domain you control, along with Calendar, Drive and admin tools. Mail from a Workspace inbox is sent through Google's own mail servers.

See also Mailbox provider, Pre-warmed inbox.

A permanent delivery failure, such as an address that does not exist or a domain that cannot receive mail, usually returned as a 5xx SMTP response. Remove hard-bounced addresses at once, because sending to them again harms your reputation.

See also Bounce rate, Soft bounce, List hygiene.

A summary score that a tool shows for an inbox or domain; each tool defines its own. On InboxesNow it is a single warm-up health score for each domain, shown in the domain's warm-up record before you buy, next to days warmed and the 7-day warm-up inbox rate.

See also Warm-up record, Warm-up.

Where a delivered message ends up: the inbox, a category tab or the spam folder. Delivery only means the receiving server accepted the message; placement is what the recipient actually sees.

See also Inbox placement test, Category tab, Spam folder, Deliverability.

A test that sends a message to a set of seed inboxes at different mailbox providers and records where each copy landed. Its result is a sample of how filters treated that message at that time, not a forecast for every recipient. See how to read an inbox placement test.

See also Seed list, Seed inbox, Inbox placement.

The trust a mailbox provider gives the IP address that delivers your mail. When you send from Google Workspace you use Google's shared sending IPs, so the reputation of your domain carries more of the weight.

See also Domain reputation, Sender reputation, PTR record.

Keeping a sending list clean: verifying addresses before you send, removing hard bounces, unsubscribes and people who complained, and treating catch-all and role addresses with care. Clean lists keep bounce and complaint rates low.

See also Bounce rate, Catch-all, Spam trap.

The service that hosts a recipient's mailbox and decides where incoming mail lands, such as Gmail, Google Workspace, Outlook or Yahoo. Each provider runs its own filters, so the same message can land differently at each one.

See also Inbox placement, Sender reputation.

A DNS record that names the mail servers that accept email for a domain. A sending domain needs MX records so that replies can reach its inboxes.

See also DNS, Google Workspace.

An unsubscribe that works in a single step from the mail client, using the List-Unsubscribe and List-Unsubscribe-Post headers defined in RFC 8058. Google requires it for bulk senders' marketing and subscribed messages.

See also Bulk sender, Spam complaint rate.

On InboxesNow, the results of the daily inbox-placement test that every inbox in stock gets, sent to seed inboxes at Google Workspace, Outlook and Gmail in the US. You see it per domain and per inbox before you buy: the inbox rate by provider over the last 7 days, as a daily strip, in the inbox placement record. It shows what the tests found, not where your own campaigns will land.

See also Inbox placement test, Seed inbox, Warm-up record.

Google's free dashboard that shows senders their spam rate, authentication results and delivery errors for mail sent to personal Gmail accounts, once a domain sends enough volume. Google asks senders to keep the spam rate reported there below 0.3%, and ideally below 0.1% (Google's email sender guidelines).

See also Spam complaint rate, Feedback loop, Domain reputation.

An inbox that has already been through warm-up before you start sending from it, so it begins with some sending history instead of none. Pre-warming removes the wait, but it does not replace a careful ramp-up and a clean list.

See also Warm-up, Ramp-up, Warm-up record.

A reverse DNS record that maps an IP address back to a hostname. Receivers expect a sending IP to have a PTR record that matches its forward DNS; with Google Workspace, Google manages this for its own sending IPs.

See also DNS, IP reputation.

Raising the daily sending volume of a new or newly connected inbox step by step instead of all at once. A gradual ramp-up lets you watch bounces, replies and complaints before volume grows.

See also Sending limit, Warm-up, Pre-warmed inbox.

A mailbox kept for testing at a particular mailbox provider, used to see where a test message lands. Seed inboxes do not belong to real prospects, so their results show how filters behaved, not how people engage.

See also Seed list, Inbox placement test.

The full set of seed inboxes that an inbox placement test sends to, usually spread across providers and account types, such as business and personal. A broader seed list gives a fuller picture of how different filters treat a message.

See also Seed inbox, Inbox placement test, Mailbox provider.

The overall trust mailbox providers give a sender, combining the reputation of the sending domain and IP with signals such as bounces, complaints and how recipients engage. It largely decides whether mail lands in the inbox or in spam.

See also Domain reputation, IP reputation, Deliverability.

The domain in the From address of your emails. Cold emailers usually send from separate domains rather than their main company domain, so a problem with outreach does not affect the main domain's everyday mail.

See also Domain reputation, Tracking domain.

The maximum number of emails an inbox sends in a day, usually set in your sequencer. Mailbox providers also enforce their own caps, but cold-email limits are normally set far below them to protect reputation.

See also Ramp-up, Sequencer.

A tool that sends multi-step email campaigns from connected inboxes, spacing first emails and follow-ups over time and usually stopping when someone replies. Many sequencers connect Google Workspace inboxes with Google sign-in.

See also Cold email, Sending limit.

A temporary delivery failure, such as a full mailbox, a server that is briefly unavailable or a message the receiver deferred, usually returned as a 4xx SMTP response. Senders retry soft bounces, but an address that keeps soft-bouncing should be removed.

See also Hard bounce, Bounce rate.

The share of delivered messages that recipients mark as spam. Google asks senders to keep the spam rate shown in Postmaster Tools below 0.3%, and ideally below 0.1% (Google's email sender guidelines).

See also Feedback loop, Postmaster Tools, Sender reputation.

The folder where a mailbox provider puts messages its filters judged to be unwanted. Mail in spam was delivered, but it is rarely seen.

See also Inbox placement, Category tab.

An address that exists only to catch unwanted mail, such as an abandoned mailbox a provider has repurposed or an address that was never used by a person. Hitting spam traps signals poor list sourcing and can lead to blocklisting.

See also Blocklist, List hygiene.

Sender Policy Framework: a DNS TXT record listing the servers allowed to send mail for a domain. Receivers check the envelope sender's domain against it, and evaluating an SPF record may cause at most 10 DNS lookups (RFC 7208).

See also DKIM, DMARC, Alignment, TXT record.

A domain, usually a subdomain of your sending domain set up with a CNAME record, that your sequencer uses for open-tracking pixels and click redirects. Using your own tracking domain keeps the links in your emails from pointing at a host that many other senders share.

See also CNAME record, Sending domain.

A DNS record that holds text. SPF policies, DKIM public keys and DMARC policies are all published as TXT records.

See also DNS, SPF, DKIM, DMARC.

Building a new inbox's sending history gradually, usually by exchanging messages with other inboxes that open them, reply to them and move them out of spam, so mailbox providers learn to trust it. See how inbox warm-up works.

See also Pre-warmed inbox, Ramp-up, Warm-up record.

On InboxesNow, the history each domain shows before you buy: days warmed, a daily warm-up chart of messages sent against messages that reached the inbox, the 7-day warm-up inbox rate and a single warm-up health score. See the warm-up record.

See also Warm-up, Health score, Pre-warmed inbox.