--- /dev/null
+require
+ [ "envelope"
+ , "fileinto"
+ , "mailbox"
+ , "subaddress"
+ , "variables"
+ ];
+
+if envelope :matches :detail "TO" "*" {
+ set "extension" "${1}";
+ }
+if not string :is "${extension}" "" {
+ fileinto :create "Extensions.${extension}";
+ stop;
+ }