cyrus marks vacation messages as duplicate

[Riccardo Veraldi]

Hello,
i have a problem.
When a user configures a vacation rule such as

# rule:[vacation]
if true
{
     vacation :days 100 "vacation test";
}


the reply vacation message is never sent to the sender of message and I 
have this in imapd.conf


Jul 24 11:48:42 iride lmtp[29631]: duplicate_check: 
<500E6F68.8080400 at gmail.com>             user.veraldi 0
Jul 24 11:48:42 iride lmtp[29631]: Delivered: 
<500E6F68.8080400 at gmail.com> to mailbox: user.veraldi
Jul 24 11:48:42 iride lmtp[29631]: duplicate_mark: 
<500E6F68.8080400 at gmail.com>             user.veraldi 1343123322 269982
Jul 24 11:48:42 iride lmtp[29631]: duplicate_mark: 
<500E6F68.8080400 at gmail.com>             .veraldi+ at .sieve. 1343123322 0
Jul 24 11:48:42 iride lmtp[29631]: USAGE veraldi user: 0.002999 sys: 
0.004999

the vacation reply message is recognized as a duplicate message and this 
is wrong.

Is this a bug ?
How can I fix this ?

any vacation messagereply is recognized as duplicate and thus is suppressed

I am using cyrus-imapd-2.4.10 on Centos 5

thank you

Rick