unable to reclaim deleted email storage

i have deleted and emptied all icloud emails from the inbox, trash, sent items and all other folders. But when looking at icloud storage used space it still says i have used 998MB. As a simple test i sent myself 20mb file and deleted it, during the test it gets added another 20mb to existing 998MB and when i delete the email it returns back to 998MB. But i can never seem to reclaim this space. Please help