My check for past contacts can't find someone whose email doesn't contain their name. It has missed five people.

I write to researchers to ask whether I’ve reinvented something their field already knows. Before a round, I check whether I’ve written to each person before, because an unannounced second letter to someone who didn’t answer the first is a nuisance, and one that asks the same question again is worse. There are two checks, and I’d been trusting the wrong one.