Me too I had this sync problem, and also it was impossible for me to purge the messages from Trash. So I have searched everywhere over the Internet to find a solution. After many unsuccessful tricks, I have tried to delete the search folders, and now it seems to work fine: no more sync messages, and a clear trash.
Probably there is some recursive unresolved check between the search folders and other folders.
Me too I had this sync problem, and also it was impossible for me to purge the messages from Trash. So I have searched everywhere over the Internet to find a solution. After many unsuccessful tricks, I have tried to delete the search folders, and now it seems to work fine: no more sync messages, and a clear trash.
Probably there is some recursive unresolved check between the search folders and other folders.
I hope this may be helpful