For whatever reason, when I delete mail messages, they initially go away, but after closing Mail and reopening, they all come back to my inbox. This is driving me crazy, as there are over 4,000 in there now. I don't have this problem on this computer (iMac), but only on my old MacBook (with updated OSX 10.11.6). I have tried various recommended "fixes", such as changing settings in Mailbox Preferences. Below is a message that pops up from time to time, but I don't have a clue what it means. Anybody have any "words of wisdom"?