Codes that describe us, not the address

Reasons originating within Emvero

A value in reason_codes may describe the address, a mail-server reply or a limit within Emvero. The service-side codes below explain why recipient evidence was not obtained. They cover selected causes, rather than every service-related condition.

Omitted, held back or unavailable probes

SMTP_PROBE_NOT_REQUESTED means the request did not ask for a mailbox probe, as with a domain check. The stage was deliberately omitted; this is not an outage report. Other checks can still provide evidence.

SMTP_PACING_REFUSED means Emvero held back an attempt at its own pacing limit. SMTP_EGRESS_UNAVAILABLE means an outbound connection resource was unavailable. SMTP_QUEUE_UNAVAILABLE and SMTP_SCHEDULER_UNAVAILABLE identify an inability to queue or schedule the work. These conditions record no refusal from the receiving server.

Work that expires before a final result

SMTP_QUEUE_EXPIRED means the SMTP work did not produce a final result within the allowed time. It may expire while waiting or after a worker starts it. The code therefore cannot tell you whether a connection occurred.

SMTP_GREYLISTED instead records a temporary refusal from the destination. An SMTP policy rejection also records a remote decision. Keeping the causes separate lets you distinguish unavailable verification work from a reply requiring interpretation.

Handling pending work and completed uncertainty

SMTP_QUEUED with pending means the work is waiting or in progress. Retrieve the same verification after retry_after_ms. A completed unknown has already reached an inconclusive result; repeatedly retrieving it does not continue pending work.

Choose a deadline and fallback for your application, such as requiring confirmation before granting account access. A separate check later may provide more evidence, but has no guaranteed outcome. The verification result guide explains how the status, action and check fields support that decision.