hosts/mermet/dovecot/sieve/global/extension.sieve

   1 require [ "envelope" , "fileinto" , "mailbox" , "subaddress" , "variables" ];
   2
   3 if envelope :matches :detail "TO" "*" { set "extension" "${1}"; }
   4
   5 if not string :is "${extension}" "" {
   6   fileinto :create "INBOX+${extension}";
   7   stop;
   8 }