Count Number of To Addresses (Addressees) in Sieve
Sieve is a mail filter language. From my understanding of https://tools.ietf.org/html/rfc5231#section-4.2 require [“fileinto”, “relational”, “comparator-i;ascii-numeric”]; if allof( address :matches “From” “test@example.com”, address :count “ge” :comparator “i;ascii-numeric” [“to”, “cc”] [“5”] ) { fileinto “\\Trash”; } This filter will move the message to trash if it has >=5 addressees and comes from test@example.com