Comment 205 for bug 883459

As per my comment above (comment #179), it would be "running the filters manually (via Ctrl-J)". I haven't yet reverted to not using filters at all and dispatching several mailing lists to their respective sub folders by using the "Move to folder" functionality.

I can also confirm that automatic filtering leads to considerably more duplicate entries than manual filtering.

I have set up a VM with a simple mail setup (one POP3 resource receiving messages from 3 mailing lists), and with automatic filtering, the issue was clearly visible with about 10 to 20% of mails affected. I have reset that one now, and switched to manual filtering, to see if I catch any duplicates here as well.