IDLE, read_all, and not delete - bad combination, skipping

Hallo Charles:

Another thing I wanted to ask before leaving this mail business in despair is:

IDLE, read_all, and not delete - bad combination, skipping

I know that you are not using IDLE, but it is a nice thing nevertheless, and I would like to keep it, so I thought it is worth asking at least once.

I was being careful and testing with "delete_after = 14", instead of "delete = true".

Are those 2 options not more or less equivalent, at least as far as IDLE is concerned? At least in a way, so that this restriction could be lifted if 
delete_after is given.

Regards,
   rdiez