These messages show up at an interval controlled by Dovecot's
imap_idle_notify_interval setting, which defaults to 2 minutes.
These messages were causing the IDLE loop to exit prematurely
because it looks like a notification response from the server.
Add a `imap::connect_starttls` convenience function, with the same
syntax as `imap::connect`, to make STARTTLS connections as easily as
IMAPS.
PR#140 removed `imap::connect_insecure` with the stated goal of
encouraging users to connect securely. With that change, users are
forced to construct their own `TcpStream`s when interacting with
non-IMAPS servers.
This change may perversely incentivise the use of insecure connections,
instead of discouraging them, as users may blindly copy-paste code
involving `Client::new` and `TcpStream`s so things "just work", without
the visual indicator of `_insecure` suggesting something is wrong.
Tangentially, [RFC 2595] encourages using STARTTLS instead of raw SSL
sockets. Ideally, we should support both options equally well.
[RFC 2595]: https://tools.ietf.org/html/rfc2595#section-7
In order to discourage folks from connecting securely, we're removing the
convenience method imap::connect_insecure.
Fear not\! For those who manage security in another way (aka a private network
or similar measures), it is still possible to connect without TLS by using the
imap::Client::new() method. See that method for examples of how to do this.
Establishes conditional compilation for all integration with the
native_tls crate in this crate. Since native_tls has been deeply
integrated into this crate for a long time, we want to maintain
backwards compatibility by making this feature part of the default.
For a consumer of this crate to "opt-out", including this in
cargo.toml:
```
[dependencies.imap]
version = 0.16.0 # Replace this with the correct version
default-features = false
```
See the conversation on Github for details on this approach:
https://github.com/jonhoo/rust-imap/issues/123
The underlying Rust library for crypto `ring` using multiple
`#[cfg_attr()]` properties together which stabilized in rust 1.33.0:
https://github.com/rust-lang/rust/blob/stable/RELEASES.md#language-4
Previously, everything else in this could be compiled with rust 1.32.0,
so this may constitute a breaking change.
