Version:           1.9.5 (using KDE 3.5.5, Debian Package 4:3.5.5a.dfsg.1-8 (4.0))
Compiler:          Target: x86_64-linux-gnu
OS:                Linux (x86_64) release 2.6.18-4-amd64

What I did:

I was using a filter on an IMAP account, to process incoming emails in INBOX. The filter would call a notification program if a certain email arrived. Due to the filter KMail starts to download the email to process it locally. One of the mails was several megabytes in size, so I cancelled the download.

What I expected:

I expected Kmail to cancel the download and leave the mails as they were.

What I got instead:

During download, Kmail seemingly marked the email as deleted, and when I cancelled the download, the message was gone, when I checked back.

What I suggest:

Is it necessary to mark the emails deleted? This should IMHO only be done AFTER a successful download of the email. Alternatively a filter which only works on the subject, sender or recepient of the email would be nice, which does NOT have to download the email. This way large mails do not take so long to be filtered. In my case this would be sufficient, since I am only looking at the Subject of the mail.