Can't get IDLE to work

[Tim Schumacher]

My understanding is I keep an IDLE handle open and receive untagged responses on the unsolicited_responses channel.

use imap;
use native_tls;

fn main() {
    let domain = "example.com";
    let tls = native_tls::TlsConnector::builder().build().unwrap();

    let client = imap::connect((domain, 993), domain, &tls).unwrap();

    let mut session = client.login("user", "pass").unwrap();
    session.select("INBOX").unwrap();

    loop {
        println!("{:?}", session.unsolicited_responses.try_recv());

        println!("enter idle");
        let handle = session.idle().unwrap();
        handle.wait_keepalive().unwrap();
        println!("exit idle");
    }
}

But I'm not getting any untagged responses (e.g. EXISTS when mail arrives).

Err(Empty)
enter idle
exit idle
Err(Empty)
enter idle
exit idle
Err(Empty)
enter idle
exit idle
Err(Empty)
enter idle

The unsolicited_responses channel is always empty. The server, Dovecot, supports IDLE. What am I doing wrong?

[Tim Schumacher]

I guess I should really upgrade to "unstable" 3.0.