Today my PC suddenly shut down because I forgot to plug the laptop into the power supply, and it ran out of batteries. Claws mail was open, and when I managed to restart the computer, after various file system checks and repairing , claws-mail loaded the messages present in the folders correctly, but when it started looking for new messages, it started to download from the first message that was on the server (and there are 17000 and more). So I think a file has been corrupted and replaced with a blank or default one. Is there a way I can tell claws-mail to ignore the first 17000 messages that are on the server and to start downloading from the 17001st onwards?
The sounds like a question for the mailing list rather a bug report. The answer is 'no'. (I assume you're talking about an imap account.) Claws won't download the messages by default, but it might depending on options you've chosen.