I posted this problem on the users mailing list in September 2007 (subject "synching Sent box again and again and again ..."). I was running 3.0.1 at the time. It's still there... ClawsMail keeps on scanning my Sent box again and again. It takes some time (2-3 minutes) with 18000 messages and you cannot do anything else in ClawsMail until it's done. Most of the time, not everytime, I click the Sent box, I get "Opening INBOX/Sent... xxx/18000". At other times it maybe only scans xxx/3000. It sometimes just starts by itself, often when I am not even actively using ClawsMail. I know because I am sitting next to the server. Colin suggested in 2007 that my IMAP server doesn't support UIDPLUS. But it does. My colleague uses the same IMAP server and the same version of CM; he never experiences this problem. I also tried accessing my email from a different PC with a freshly set-up ClawsMail (same version). The problem did not appear. However, I am not using this other PC actively, so I can't say for sure. Colin asked in 2007 whether I had any processing rules in place. I don't. I deselected 'scan for new email' on the Sent box. It does not make a difference. This is really getting to me. Is there anything I can do to debug this?
try upgrading to the latest release, re-open if it continues.
I upgraded to Vlawsmail version 3.5.0 and the problem persisted. What solved the problem for me was migrating from courier-imap to dovecot-imapd. From the day the server operated on dovecot-imapd, the sent-box was never re-scanned again. However, there is obviously a problem in the claws-mail and courier-imap constellation.
See comment #1. (3.5.0 was released over 2 and a half years ago and there have been 14 releases since then)