How can I set up email (mostly yahoo) so that no matter which device I delete an email on, it will be deleted on the other? I finally switched to Android from Apple, and I've tried setting the email account as both premium and not, and it either stays independent when deleted (not deleted on the server), or it's just downloaded again. K-9 seems to make them stay independent, but there's a lot of settings. Is there anything I can do so that if I delete a message on either the mail site or the app, it will be deleted on the other?

Basically, if you're aware of how the mail app works on the iphone, etc, I want it to behave like that.

EDIT: I found out how to do it in K-9 (change the 'when i delete a message' setting), but is there a way to do it stock?
As roxan already pointed out: What you want is IMAP for all your E-Mail accounts, configured with an Android client (e.g. K-9 Mail).