Knock on the door even if you think nobody’s home. You’d be shocked how often someone is.

Knocking costs almost nothing, and people badly overestimate the odds of nobody being home. The email you have written off as obviously ignorable gets answered more often than you would guess, because hardly anyone is asking and a direct question is rare. Your estimate is not built on data, it is built on not wanting to find out.

Send the message you already dismissed as pointless. Keep it short and specific, with one clear ask in it. Send five, and treat silence as ordinary rather than as an answer about you.