Sourcing audits are won and lost in the first week of email correspondence. Anyone can pass a polite first reply. The signal is in how quickly things degrade — or don't — by the third exchange.
Email one — the spec test
Send a tight RFQ with three specs intentionally mis-stated (wrong material, wrong MOQ, wrong tolerance). The factories that copy-paste your spec into a quote without questioning anything are the ones who'll ship you the wrong thing six months from now. The factories that flag all three are your shortlist.
Email two — the timeline test
Once you've shortlisted, ask for a sample within 14 days at your spec. Watch what they propose. A real factory has a calendar — they'll come back with a date, a tracking number plan, and a Q&A list. A trading company will say "no problem, very fast" without a single specific.
Email three — the QC test
Ask for the full QC checklist they'll run on your specific SKU. Not their generic ISO doc. Your SKU. Factories with real QA capability send you a one-page checklist by Tuesday. The rest go quiet, then send a vague PDF on Friday. That's your answer.
The shortcut
If a factory passes all three emails, the sample is usually right too. Sample failures correlate almost perfectly with sloppy email replies. We've yet to find an exception across 60+ verified factories in our network.