I recently accepted installation of the latest version of eM Client. Prior to this I had the last most recent version. Ever since that update, I am having difficulty deleting emails from my Inbox. When I delete, they disappear only briefly, then come right back up in the Inbox.
It may be that the message cache has become corrupted.
You can right-click on the Inbox and choose Properties > Repair. If your account is with Gmail or Gsuite, right-click on the All Mail folder instead.