broken sync: IMAP -> local -> IMAP

[Timo Nentwig]

Hi!

I do sync between 2 IMAP servers. Actually, it's a one-way backup sync from 
remote to local. I run into validility errors all the time with by INBOX.Sent 
folder. Tried all kinds of file deletions (last attempt: find .offlineimap/ | 
grep Sent) and resyncs and stuff and know have the behaviour that all mail is
downloaded from remote to local and then sent 
back to remote (and then probably sync'ed back again, i.e. duplicating all 
mails).

Help!