icloud Mail account (imap) on mac is immediately deleting mail on iPhone

hello

my icloud Mail account (which is imap) on mac is immediately deleting mail on iPhone (which is also imap).

here is what is happening:

when an email is sent to my icloud (@mac.com) account, both my mac imap Mail account and my iPhone imap icloud account are able to download it.

but as soon as the mail is downloaded fully to the mac, then it is removed from the iPhone.

only thing is, i am not deleting it - some setting is deleting it. but both accounts were automatically configured without my entering anything except name, account and password (on mac).

how do i get it to stop deleting mail automatically from the server?

thanks