fetchmail+sieve: losing mail if cyrus is down

[cyrus at nitwit.de]

Hi!

I periodically fetch mail from my ISP via fetchmail and sort it into my IMAP 
box via sieve. For some reason (reiserfs is crap?) it sometimes happens that 
cyrus needs to recover DB and it not available during this time - but 
fetchmail/sieve keep on going their job, of course.

So, it happens that that mail is being lost. I thought there would be some 
buffering queue or somthing but obviously it is not.

1) Are those mails really lost?
2) What can I do about that problem?

Thanks
Timo