How GTM Inboxes uses this term
GTM runs IMAP probes as part of go-live connectivity preflight and seed-mailbox polling, and composes IMAP metadata into inbox readiness alongside SMTP checks.
How IMAP and SMTP smoke tests differ
An SMTP smoke test proves the mailbox can submit a controlled message. An IMAP smoke test proves the mailbox can be opened and read. Launch-safe inboxes need both, because sending without read access breaks reply and evidence workflows.
Where GTM runs it
IMAP probes run inside operator connectivity preflight and the seed-mailbox pollers that read controlled test messages. Results are recorded with redacted errors and never expose mailbox contents or credentials.