If a mail just downloaded is moved by a filter to a different folder then there is a good chance that it will re-appear again in the original folder at the next update
It does not happen with all the accounts or all the filtered messages. However if a message is affected then it's 100% reproduceable: it will be duplicated at every folder update (forever?).
I experience this problem in 4.7.90 (4.8 beta2).
If a mail just downloaded is moved by a filter to a different folder then there is a good chance that it will re-appear again in the original folder at the next update
It does not happen with all the accounts or all the filtered messages. However if a message is affected then it's 100% reproduceable: it will be duplicated at every folder update (forever?).