uChecker

uChecker is a list checker you run on a file you already have. Drop a .txt or .csv, one job can take up to 9 million addresses at about 3200 a minute, and you skip the pre-clean. Results come back Good, Bad and Risk. Unknown never counts as valid. The full SMTP reply is stored. Use app.uchecker.net, api.uchecker.net/docs, @uchecker_bot, or https://uchecker.net/mcp. Thirteen DNS tools stay free at https://uchecker.net/tools.