Glossary
Glossary
42 email and agent-sending terms, each defined in one sentence and linked to the page where it decides a send.
- Appeal
A request for a person to review a pause or a sandbox. Filing it does not resume sending.
- Approval queue
Sends held for a person to approve or reject. Approving sends the held message.
- Batch
Several different messages in one request. One item can fail on its own.
- Block bounce
A refusal on reputation or content. The address itself is not the cause.
- Budget period
The window a key's send budget refills on: hourly, daily or monthly.
- Complaint rate
The share of delivered mail that recipients mark as spam, judged by the ladder.
- Dead letter
A webhook delivery kept after the retries are used up, so it can be replayed.
- DKIM alignment
The signing domain and the From domain match, or they share one organisation domain.
- DMARC alignment
A pass when either DKIM alignment or SPF alignment passes for the From domain.
- Enforcement ladder
Warn, then pause, on bounce rate and complaint rate. One step per check.
- Feedback loop
A mailbox provider's notice that a recipient marked the message as spam.
- Fix field
The sentence on every refusal that says what to do next and which call does it.
- Full access
A key that can manage the account as well as send. It still cannot raise its own budget.
- Hard bounce
A permanent bounce: the address does not exist, and it is suppressed.
- Human action required
A change only a person can make. A key cannot raise its own limits.
- Idempotency key
The caller-chosen key that makes a retry of the same request return the first result.
- Inbound thread
Messages grouped by their ids and reply headers. Receiving at your domain is not open yet.
- Kill switch
A pause that stops a key, or every key, from sending on the next request.
- List-Unsubscribe
The header a mailbox shows as unsubscribe. Topic sends and broadcasts carry one.
- Loop detection
A hold on a near-identical repeat, and on a send into an inbox a window has collapsed onto.
- MCP scope
A permission granted to a connected assistant. Sending spends the budget on that connection.
- Overage
Emails past the inclusion, only when you have turned them on and set a ceiling.
- Plan inclusion
The emails included in the plan for the month. A key budget cannot exceed it.
- Policy bounce
The address is real. This message was refused for size, an attachment, or suppression.
- Preflight
A check that reports what a send would do, without sending it or recording a hold.
- Rate ceiling
How many recipients one key may accept in a single minute.
- retry_after_seconds
The wait, in seconds, on a refusal that waiting can cure. Absent when waiting cannot.
- Return path
The MX and TXT on your domain that receive bounces and keep the envelope aligned.
- Sandbox
An account limited to sending to its own verified domains until a person reviews it.
- Scheduled send
A message accepted now and delivered at a later time you set. Counted at accept.
- Sending access
A key that sends and reads what it sent. It cannot edit the account.
- Sending domain
A domain you verify, then send from. An unverified From is refused.
- Signature tolerance
How old a webhook timestamp may be before the delivery is rejected as a replay.
- Simulator address
An address that accepts a send, costs nothing, and delivers to nobody.
- Soft bounce
A temporary refusal. The message can be tried again later.
- SPF alignment
The envelope domain and the From domain match, or they share one organisation domain.
- Standing
The trust state for transactional mail and for marketing mail, published for the account.
- Stream
Transactional or marketing. The ladder can pause one and leave the other sending.
- Suppression
An address we will not mail. A later send to it is refused.
- Topic
A named kind of mail. A contact who opts out of it is skipped on sends of that kind.
- VERP
An envelope sender on your return-path host that names the message a bounce belongs to.
- Webhook signing
A timestamp and a signature over the raw body, checked before the payload is parsed.