BT mail account not syncing

i am having issues with my BT mail account not syncing between my iPad and iPhone. I have recently moved from Yahoo mail to BT mail but still kept my same BT mail Address. The emails are coming through on both devices but when you delete one from either device it does not update on the other. Also when I set up sub folders in the inbox it is not pulling these between devices.

Any help would be greatly appreciated!

Thanks