As have others, I often get two copies of sent messages instead of one. At a previous discussion, https://support.mozilla.org/en-US/questions/1151306, someone suggested going to tools > Account Settings > Copies & Folders and disabling the "Place a copy in" option. This solution doesn't solve this problem for me. I use 4 email accounts, all of them iMap. On one of them I have a folder/subfolder hierarchy of: <account>/<home>/Email 2017/Sent 2017. I want copies of ALL sent messages from all four accounts to be stored in this folder, and ONLY this folder. To implement this, for each account I originally checked the place-a-copy-in box, and for "Other:" set the path to the Sent 2017 subfolder. This does put a copy there, but a duplicate copy is being put in the Sent folder of the sending (Gmail) account. THIS is the behavior I want to turn off. Disabling the place-a-copy option turns off storing the message in the Sent 2017 folder. How does one disable storing the message in the sending account's Sent folder instead?