Comment 3 for bug 883459

From what I can tell, this has to do something with filters - as it happens only on accounts I have set up filters for (e.g., if "Anywhere in Header" contains "X-Launchpad-Hash", move email into "KMail Folders/Launchpad").

Emails get duplicated usually when new mail arrives.

Sometimes emails resurrect after I delete them.

This makes me think that when email is moved by the filter rule, KMail does not actually delete it - just hides it. Then when new mail arrives, it finds that "semi-deleted" email, applies a filter to it and now I get a duplicate of the existing emails.

I often see a warning "KMail Folders: Cannot modify emails in folder" (the warning is in Russian so my translation is approximate).