Reject NPS surveys before they reach your inbox

nps-killer.sieve

require ["comparator-i;ascii-numeric", "reject"];

/**
 * Emails containing Net Promoter Score surveys
 */
if allof (
    header :comparator "i;unicode-casemap" :contains "Subject" ["How likely are you to recommend", "How did we do?", "how was your recent delivery?", "Two Quick Questions", "Tell us how we did!"])
{
    reject "NPS surveys are not accepted";
}