Jan 20 10:01:33 lda(account1): Info: sieve: msgid=<52DCF32D.7030406@companieshouse.gov.uk>: stored mail into mailbox 'Junk'
Jan 20 10:01:33 lda(account2): Info: sieve: msgid=<52DCF32D.7030406@companieshouse.gov.uk>: stored mail into mailbox 'Junk'
Jan 20 10:14:37 lda(account3): Info: sieve: msgid=<52DCF761.5000603@rbs.co.uk>: stored mail into mailbox 'Junk'
Jan 20 10:14:40 lda(account4): Info: sieve: msgid=<52DCF761.5000603@rbs.co.uk>: stored mail into mailbox 'INBOX'

From sieve log it's quite clear that it places the same message that was sent to two different accounts into different folders. The one  that is put inside inbox is being identified as spam, according to the header, but still goes to inbox:

X-Spam-Flag: YES
X-Spam-Score: 6.119
X-Spam-Level: ******
X-Spam-Status: Yes, score=6.119 tagged_above=2 required=4 tests=[BAYES_99=3.5,
    RCVD_IN_BRBL_LASTEXT=1.449, RCVD_IN_XBL=0.375, RDNS_NONE=0.793,
    SPF_FAIL=0.001, TO_NO_BRKTS_NORDNS=0.001] autolearn=no

Here is the script:

require ["fileinto"];

# rule:[Move Spam to Junk Folder]
if header :is "X-Spam-Flag" "YES"
{
    fileinto "Junk";
    stop;
}

Zhang
Thanks I was looking this answer
But is there possiblity to have this spam settings always? If some one create first rule in roundcube, rule spam still work?