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fix(verifier): mx_unreachable was mislabeling live big-ISP mailboxes

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The verifier returned (True, 'mx_unreachable') when it couldn't complete a port-25
probe to ANY MX — marking 438,163 addresses email_verified=TRUE. But these are NOT
dead: they're dominated by Comcast (13.7k), AT&T/SBCGlobal (13.5k), Verizon, Cox,
Charter, Frontier, etc. — major ISPs that deliberately tarpit/refuse probes from
unknown IPs. Confirmed from prod: comcast MX connects + returns 220. The probe
failure ≠ undeliverable.

Fix: return (False, 'mx_probe_blocked') — MX exists, deliverability UNKNOWN, must
be confirmed by a real send. Excluded from PW campaigns; prime burner-verification
target (burner_list_verify upgrades it to send_confirmed on delivery). Existing
438,163 mx_unreachable rows reclassified in prod to mx_probe_blocked / verified=FALSE.
This commit is contained in:
justin 2026-06-17 05:48:08 -05:00
parent c2737f2001
commit 1eb29f80be
2 changed files with 14 additions and 4 deletions
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7
scripts/burner_list_verify.py
View file

@ -48,8 +48,11 @@ STATUS_RE = re.compile(r"status=(\w+)")
# Results we are allowed to UPGRADE to 'send_confirmed'. We never overwrite an
# explicit smtp_valid (already best) or a hard_bounced (worse signal wins).
UPGRADABLE = ("catch_all_domain", "catch_all_detected", "mx_unreachable",
"smtp_temp_error", "smtp_unknown_451", "smtp_unknown_450")
# 'mx_probe_blocked' is the big-ISP pool (Comcast/AT&T/Verizon/etc.) the SMTP
# probe couldn't reach — these are the prime burner-verification targets.
UPGRADABLE = ("catch_all_domain", "catch_all_detected", "mx_probe_blocked",
"mx_unreachable", "smtp_temp_error", "smtp_unknown_451",
"smtp_unknown_450")
def scan_log(log_path: str) -> tuple[set[str], set[str]]:

11
scripts/workers/email_verifier.py
View file

@ -162,8 +162,15 @@ def verify_email(email: str) -> tuple[bool, str]:
LOG.debug("SMTP error for %s via %s: %s", email, mx_host, e)
continue
# Couldn't connect to any MX — domain exists but server unreachable
return True, "mx_unreachable"
# Could not complete an SMTP probe to ANY MX, even though valid MX records
# exist. This does NOT mean the address is dead — large providers (Comcast,
# AT&T/Yahoo, Verizon, Cox, Charter, etc.) deliberately tarpit / refuse port-25
# probes from unknown IPs as an anti-spam measure, so the probe times out on
# millions of perfectly deliverable mailboxes. We therefore return
# email_verified=FALSE with 'mx_probe_blocked': the domain has mail servers but
# deliverability is UNKNOWN and must be confirmed by a real send (burner-domain
# verification → 'send_confirmed'). Campaigns must NOT treat this as sendable.
return False, "mx_probe_blocked"
def verify_table(table: str, limit: int | None = None, dry_run: bool = False, where: str | None = None) -> dict: