The IMAP mailbox that Dovecot sets up has no SENT folder or TRASH folder. How do I set those up? Is there a way to place them outside of the INBOX hiearchy? I want to make sure that these folders work with the iPhone email client or any other mobile email client.
So just to be aware, there's no "standard" here, different clients sometimes use different folders for Sent, Drafts, Trash etc.
Saying that, if you have a standard for your clients to use (or you're just using one client), you can auto-create and auto-subscribe clients to folders.
See the autocreate plugin