I've also heard of some actual mbox corruption from one large installation, but I don't know if it really was Dovecot's problem as I've never heard of it from others. Might have been some problem related to their specific environment.

I have also had a similar problem where there was partial curroption of an mbox folder. After that point in time, I could not properly read some messags using Openwebmail. I did not have time to fully investigate the exact cause and the exact form of the curroption, but I did want to let you know that it is an issue. Thanks, Joe