Inbound-only mail data cannot distinguish newsletters from relationships

When building a warm-contact graph from a mail store, an analysis that runs before the Sent folder syncs silently yields inbound-only results that look complete but rank vendors, alerts and mailing lists at the top. The tell for a mailing list rather than a real relationship is many distinct sender addresses at one domain combined with zero meeting invites, since a genuine contact concentrates on one or two addresses and usually has calendar traffic. Sent is the ground truth for warmth because outbound proves intent while inbound only proves someone had the address. In Thunderbird IMAP specifically, non-INBOX folders stay at their roughly 1.2KB stub size until the user clicks them, so verify each folder mbox has real size before trusting any ranking built from it.