I only pick leads whose email runs on Google, because Outlook and Yahoo bury new senders. I tested that on my own mail. New inboxes need 2–3 weeks of warmup, and nobody can skip it. Where an email lands also depends on your copy and volume, so I don't promise the inbox. I promise every check passing and a mail-tester score of 9/10 or better, or I fix it until it is.