Knowledge base
deliveriescriticalcounterMessages a receiver accepted — the one unambiguous number in the set.greylistedcriticalcounterTemporary refusals — the messages that will be tried again.allgreylistedimportantcounterEvery temporary refusal, whether from the receiver, from us, or inherited.attemptsimportantcounterAttempts started in this second — not results, and deliberately not the denominator of any rate.errorsimportantcounterPermanent SMTP refusals, plus connections lost mid-conversation.failuresimportantcounterEleven error counters added together — excluding unassignable and strange, both of which are real failures.noipsimportantcounterDestinations that resolved to nothing — the list problem, not ours.norecipientsimportantcounterJobs that arrived without a usable recipient — our bug, not the receiver's.parkedimportantcounterMessages moved out of memory into a temporary per-destination queue because a limit is holding them back.strangeimportantcounterThe engine's bucket for failures it cannot classify — and the only counter excluded from every total.successimportantcounterDeliveries over finished messages in this second — not over attempts.unassignableimportantcounterMessages with no usable sending address for their destination — a configuration failure that the main failure total leaves out.untriederrorsimportantcounterMessages failed without an attempt, because the engine already knew the attempt would fail.untriedgreylistedimportantcounterMessages deferred without an attempt, on the strength of a recent temporary refusal.activecounterThe connections actually sending — computed, not measured.allerrorscounterSeven error counters summed — permanent failures only, so it excludes expiries, missing recipients and everything greylisted.connectionscounterAll outgoing SMTP connections the node holds, in any state.connectscounterHow many times the engine had to open a fresh SMTP connection.errorRatecounterThe complement of the success rate, over the same denominator.expiredcounterMessages that ran out of time rather than out of attempts.forcederrorscounterMessages we failed on purpose, permanently.forcedgreylistedcounterMessages we deferred on purpose with a temporary code.nobodycounterThe body could not be fetched from the message store, or personalisation failed.notsecurecounterMessages refused by our own TLS requirement, not by the receiver.queuecounterMessages the engine is holding, read from the broker and not yet finished.queuedcounterEverything the engine is holding — in memory, assigned or parked.reusescounterMessages that went down a connection already open — the measure of how well pipelining works.totalErrorscounterHow much of the node's finished traffic this slice failed — a share, not a rate.totalSuccesscounterNot a success rate at all: how much of the whole node's finished traffic this slice accounts for.assignedcounterMessages waiting on a connection that is still being established.bytescounterThe volume actually handed to receiving servers.connectingcounterConnections in handshake, or open but with nothing to send yet.idlecounterOpen connections with nothing to send, kept for the next message.