[Dovecot] Problem with sieve. dovecot 2.0.17

[Eliezer Croitoru]

Since I have lots of filtering rules in thunderbird I was thinking of 
using sieve instead.
I want to filter incoming mail into subdirectories.
like "from" store at folder "old".
the script is:
require ["fileinto", "envelope"];
if envelope :is "from" "eliezer at test.dom" {
   fileinto "old";
} else {
   # The rest goes into INBOX
   # default is "implicit keep", we do it explicitly here
   keep;
}

the result is that the mail is stored in two folders instead of just 
one, INBOX and old.
the logs shows:
Oct 23 17:12:26 lda(eliezer at ngtech.co.il): Debug: sieve: executing 
script from /home/vmail/domain/eliezer/home/.dovecot.svbin
Oct 23 17:12:26 lda(eliezer at test1.dom): Info: sieve: 
msgid=<5086B3C9.5030909 at test.dom>: stored mail into mailbox 'INBOX'
Oct 23 17:12:26 lda(eliezer at test1.dom): Info: sieve: 
msgid=<5086B3C9.5030909 at test.dom>: stored mail into mailbox 'old'

from unknown reason(or I didnt understood how sieve works?)

plugin section from dovecot -n

plugin {
...
   sieve = ~/.dovecot.sieve
   sieve_dir = ~/sieve
   sieve_extensions = +vnd.dovecot.debug +imapflags +relational 
+comparator-i;ascii-numeric
}

Thanks,
Eliezer