Each term gets one plain sentence, then the part that costs money. Jump to any of them.
A DNS record listing which servers may send mail using your domain.
Where it bites: Two SPF records break the check completely: the receiver does not pick one, it fails both. The lookup limit is ten, and going over turns the result into an error that counts as unauthenticated.
A cryptographic signature added to each message, verified against a public key in your DNS.
Where it bites: Without it, forwarded mail loses its SPF result and fails DMARC. That is why newsletters break when somebody forwards them to a colleague.
A policy saying what to do with mail that fails SPF and DKIM, plus where to send reports.
Where it bites: Since February 2024 Gmail treats bulk mail without DMARC as unverified. Policy none means you are watching, not protecting: anyone spoofing you is delivered exactly like you are.
The requirement that the domain in the visible From address matches the domain that passed SPF or DKIM.
Where it bites: This is where most setups fail while every individual check shows green. Passing SPF for your sending tool's domain does nothing if your From address is your own.
A standard that shows your logo beside your mail, once DMARC is at quarantine or reject.
Where it bites: It only works after the authentication is already correct, which is the real reason to care about it.
The share of messages rejected outright by the receiving server.
Where it bites: Hard bounces mean the address does not exist. Above roughly 2% on a send, mailbox providers start treating the list as unmaintained.
How often recipients press the spam button, as a share of delivered mail.
Where it bites: Google's bulk sender guidelines set 0.3% as the line you must never reach and recommend staying under 0.1%. It is measured per domain, not per campaign.
An address that never opted in, used by providers and blocklists to catch senders who buy or scrape lists.
Where it bites: A recycled trap is an old real address that was abandoned and reactivated. Sending to one proves you never clean your list.
Raising volume gradually on a new sending domain so providers can build a reputation for it.
Where it bites: There is no fixed schedule that works everywhere. What matters is that early volume goes to people who actually open, not to your whole list.
A provider's running judgement of your domain and IP, based on complaints, bounces and engagement.
Where it bites: It belongs to the domain more than the tool. Changing email platform does not reset a bad reputation.
Removing addresses that bounce, never open, or were never confirmed.
Where it bites: Cutting a list usually raises delivered volume, because engagement rises and the provider stops filtering. That is counterintuitive and it is the most common quick win.
The event that starts an automation: a form, a purchase, a tag, a date.
Where it bites: Event driven triggers fire in seconds. A nightly batch turns every sequence into a next day sequence, and most people do not know which one they have.
A deliberate pause between messages in a sequence.
Where it bites: The wait is a decision, not a delay. Twenty minutes after an abandoned cart and two days after a webinar are both correct, for different reasons.
Splitting a sequence by a condition, usually whether the previous message was opened or acted on.
Where it bites: One condition after the first email is the cheapest improvement in most accounts. Without it, people who already bought get asked to buy again.
A fixed series of messages sent on a schedule after a trigger.
Where it bites: Fixed schedules are simple and blunt. They work for onboarding and fail for anything where the person's behaviour should change what comes next.
Messaging organised around where somebody is in their relationship with you rather than around campaigns.
Where it bites: The practical test: can you say what a person receives on day three of being a customer? If the answer is a campaign calendar, it is not lifecycle.
Assigning points to behaviours so sales can rank who to call first.
Where it bites: A model with guessed weights predicts nothing and looks precise. Decay matters more than the weights: somebody who visited pricing yesterday is not the same as somebody who visited a year ago.
Marketing qualified lead: somebody marketing considers ready for sales contact.
Where it bites: The term causes more arguments than it solves unless both teams sign one sentence defining it. Without that, marketing counts forms and sales counts calls worth making.
The rules that decide which person or team receives a new lead.
Where it bites: A shared inbox is not an owner and a rota is not an owner. If a warm lead can sit two days without anybody being responsible, it will.
Requiring the subscriber to confirm by clicking a link in a first email.
Where it bites: It costs you list size and buys you deliverability, provable consent and far fewer spam traps.
A header letting the mail client remove somebody without opening your page.
Where it bites: Required for bulk senders to Gmail and Yahoo since February 2024, and it must be honoured within two days.
Addresses you must never send to again: unsubscribes, complaints, hard bounces.
Where it bites: It has to live above the tool. Moving platform and losing the suppression list is how companies mail people who unsubscribed two years ago.
Name the term and your domain. We reply with what to fix first and why. No cost, no call.