Fix 1 (consumer mx: exclusion) and Fix 3 (pw-mx-tag cron) live as of 9eeed47.
Verified: warmup pool 353,909 after fix (not starved), mx:yahoodns.net cap=0
during warmup, cron tags idempotently. Fix 2 (NULL bucket cap) deferred.
Analysis-only plan (no code shipped). The trucking builder's warmup excludes
big receiving operators (Google/MS/Proofpoint/...) by mx_provider, but three
holes let throttling/consumer MX through during the day<=30 window:
1. Consumer operators tagged with the "mx:" prefix (mx:yahoodns.net = 283,113
sendable carriers, mx:icloud.com = 24,985, comcast/charter/centurylink/...)
are NOT in BIG_MX_OPERATORS, so they slip both the exclusion and the throttle.
These are custom domains whose MX points at Yahoo/iCloud -- invisible to the
literal-domain blocklist, only catchable via MX tagging. Biggest hole.
2. 315,892 untagged (NULL) sendable carriers are sent to unvetted (kept by design
for anti-starvation, but uncapped).
3. mx_tag_carriers.py is on no cron, so the NULL backlog never drains and new
FMCSA imports stay untagged -- slowly re-opening gaps 1 and 2.
Plan proposes: CONSUMER_MX_OPERATORS set folded into exclusion+throttle (behind
the existing MAIN_SKIP_BIG_MX switch), a bounded cap on the NULL bucket, and a
daily pw-mx-tag cron. Includes live numbers, validation steps (dry-run selector
diff, no sends), and open decisions (re-introduction ramp, permanent vs warmup-
only exclusion for Yahoo/iCloud custom domains).
