For some days I have been using the latest somehow fixed version of the email app disclosed by admin diajent in a bug section which is nicely working now, no more overlapping issues, no waiting issues. Since I am using this trying to find any bug or errors and urging others too to test the latest email app.

Collaborative trials will help flyme devs to know unknown bugs and also will help flyme to provide us a better service. You can download this app from Google drive Here published couple of days ago in this thread.
Thanks.