Email deliverability — plain English.
Definitions for every term you will encounter: authentication protocols, reputation signals, blocklists, and the mechanics of inbox placement. No jargon, no padding.
- Entry 01Deliverability
What is DMARC?
DMARC is a DNS-published email authentication policy that instructs receiving mail servers to reject, quarantine, or allow messages that fail SPF and DKIM alignment.
Read definition - Entry 02Deliverability
What is SPF?
SPF is a DNS TXT record that authorizes specific mail servers to send email on behalf of your domain — receiving servers reject or flag mail from servers not on the list.
Read definition - Entry 03Deliverability
What is DKIM?
DKIM is a cryptographic email signing protocol — your mail server signs outgoing messages with a private key; receiving servers verify the signature using a public key published in your DNS.
Read definition - Entry 04Deliverability
What is an email blocklist?
An email blocklist is a real-time database of IP addresses and domains reported for spam activity — receiving mail servers query these lists to decide whether to accept, filter, or reject inbound messages.
Read definition - Entry 05Deliverability
What is email deliverability?
Email deliverability is the measure of how reliably your outgoing messages reach recipients' inboxes — as opposed to being filtered to spam, deferred, or rejected entirely.
Read definition - Entry 06Deliverability
What is sender reputation?
Sender reputation is a score assigned by mailbox providers (Gmail, Outlook, Yahoo) to your sending domain and IP, based on behavioral signals like complaint rate, bounce rate, and engagement — it determines whether your email lands in the inbox or spam.
Read definition - Entry 07Deliverability
What is an email bounce?
An email bounce is a delivery failure: the receiving mail server returned an error code indicating the message could not be delivered — either permanently (hard bounce) or temporarily (soft bounce).
Read definition - Entry 08Deliverability
What is a spam trap?
A spam trap is an email address that was never used to sign up for anything — it exists solely to catch senders who harvest addresses, buy lists, or fail to remove stale addresses, and a hit can trigger immediate blocklist listings.
Read definition - Entry 09Deliverability
What is email warm-up?
Email warm-up is the practice of starting with very low send volume on a new domain or IP and increasing it gradually over several weeks to build a positive sending history before scaling to full volume.
Read definition - Entry 10Deliverability
What is an MX record?
An MX (Mail Exchange) record is a DNS record that points to the mail server(s) responsible for receiving email for a domain — without it, email addressed to your domain has nowhere to go.
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See how your domain actually scores.
A definition tells you what DMARC is. The free audit tells you whether yours is at enforcement, whether your SPF lookup count is safe, and whether your sending domain appears on any major blocklist — in under a minute.