PR for the 0.10.0 release.

There are still a few changes I want to get in, so at the moment this is a draft:

• [x] Part 2 of 2 of the AsyncSmtpConnector refactor. #545 #560
• [x] Seal lettre::transport::smtp::Error so that we don't expose libraries like r2d2, webpki ecc. since they aren't stable yet. The idea is to make it like reqwest::Error #564
• [ ] ~~Remove lettre::transport::stub, we can always add it back later if people need it.~~
• [x] Add integration tests for the async versions of the transports (we can probably copy them from the sync version) #561
• [x] High level method for attaching files #511 #495
• [ ] Go through the docs again and see if we forgot to fix anything
• [ ] Anything else I might be forgetting?

Issues for a future 0.10.n release:

• #576

Issues for a future 0.11.0 or 1.0 release:

• ~~#474 (a workaround is explained in the comments)~~
• #458

In the meantime we can use this PR to evaluate what else should go in the changelog.

Closes #467 Closes #356 Closes #245 Closes #200 Closes #501 Closes #544 Closes #427 Closes #511 Closes #699 Closes #790 Closes #727 Closes #707 Closes #605

Describe the bug When updating from lettre 0.10.0-alpha.4 to 0.10.0-rc.2, the Content-Disposition header handling was replaced with an own implementation in #601.

When setting an attachment filename with the new attachment API containing an umlaut like "Töööst.pdf", it will also encode the filename= part of the header. Example output:

Content-Disposition: attachment; =?utf-8?b?ZmlsZW5hbWU9IlTDtnN0?=.pdf

My email client no longer shows any filename for the attachment :)

This is how I handled an utf-8 based filename for attachments in lettre 0.10.0-alpha.4:

parts = parts.singlepart(
    SinglePart::base64()
        .header(header::ContentType(
            "application/pdf".parse().unwrap(),
        ))
        .header(lettre::message::header::ContentDisposition {
            disposition: DispositionType::Attachment,
            parameters: vec![DispositionParam::Filename(
                Charset::Ext("utf-8".into()),
                None,
                pdf.filename.as_bytes().to_vec(),
            )],
        })
        .body(raw_pdf),
);

This resulted in this header:

Content-Disposition: attachment; filename="Töst.pdf"

Also not ideal since it does not specify the character encoding, the mail client assumed utf-8 though.

I'm unsure how the attachment API for non utf-8 filenames is best exposed in lettre.

Related read: https://blog.nodemailer.com/2017/01/27/the-mess-that-is-attachment-filenames/

a new module was created to provide dkim_signing capabilities to message given a configuration. I tried to make as few changes as possible in Message struct. It's rust beginner work, so comments are more than welcome. Using existing dkim create was on option but I did not find easy to implement it in the existing code base. I started from the RFC and implement it from scratch. Choices that were made to keep it manageable to develop quickly.

• Only sha256 hashing with rsa signatures is implemented
• Repeating headers to be signed not supported since multiple headers does not seem to be implemented in the lib
• l dkim paramtere was not implemented to keep things simple
• the sign function is not tested yet, didn't find a way to do so properly using another implementation to check it

The current release on cargo only requires native-tls 0.1. native-tls 0.1 requires openssl 0.9 which does not support openssl 1.1.1. This means any packages depending on lettre do not compile on systems that have the most up-to-date openssl system library.

native-tls has already been updated on master. Publishing a release would allow systems with system library openssl 1.1.1 to compile their projects.

Message body looks like this:

--OgB3T6zj15dxZcwauJuVwXGLlqwRXR Content-Type: text/plain; charset=utf-8

Hello world.

--OgB3T6zj15dxZcwauJuVwXGLlqwRXR--

in every email client.

To Reproduce It always happens this way. Can't get it to stop.

Expected behavior I only want to see the message body "Hello world."

Environment (please complete the following information):

• 0.9.3
• Local: Windows 10
• SMTP Server: Kerio Connect 9.1 on Windows

This makes it more useful as a testing tool as it now allows you to retrieve all messages sent via this transport.

I don't really like the

message_log: Arc::new(StdMutex::new(vec![])),
#[cfg(any(feature = "tokio1", feature = "async-std1"))]
message_log_futures: Arc::new(FuturesMutex::new(vec![])),

construct but I didn't find a better way.

• [x] make a doc pass (fix outdated docs, fix formatting for some code samples, like some from SMTP transport, which look broken ecc.)
• [x] prepare a meaningful changelog, and some migration instructions from 0.9 to 0.10
• [x] Pool customization (https://github.com/lettre/lettre/pull/463#discussion_r485186473) (PR #479)
• [x] danger_accept_invalid_hostnames for TlsParameters (see gitter discussion) (PR #471)
• [x] Configure a custom root certificate in TlsParameters (PR #473)
• [x] Replace usage of unwrap in doctests (see https://rust-lang.github.io/api-guidelines/documentation.html#c-question-mark) (PR #491)
• [x] Replace the IntoCredentials trait with From (PR #478)
• [x] Upgrade base64 crate for us and hyperx (PR #477)
• [x] Adding a README to the examples folder, describing what every example does (PR #489)
• [x] Reworking the CI configuration and using cargo-hack to test every combination of features
• [x] Rethink top-level exports (PR #487)
• [x] Move Envelope into address (PR #488)
• [x] fix lettre::transport::smtp examples (PR #536)
• [x] Reconsider features enabled by default
• [x] get https://lettre.rs ready (https://github.com/lettre/lettre.rs/issues/4)
• [x] Rethink errors in lettre::smtp::error::Error
• [x] Tests for AsyncSmtpTransport

error[E0432]: unresolved import `nom::simple_errors`
 --> /root/.cargo/registry/src/github.com-1ecc6299db9ec823/lettre-0.8.2/src/smtp/response.rs:5:10
  |
5 | use nom::simple_errors::Err as NomError;
  |          ^^^^^^^^^^^^^ Could not find `simple_errors` in `nom`

error[E0433]: failed to resolve. Could not find `simple_errors` in `nom`
  --> /root/.cargo/registry/src/github.com-1ecc6299db9ec823/lettre-0.8.2/src/smtp/error.rs:40:18
   |
40 |     Parsing(nom::simple_errors::Err),
   |                  ^^^^^^^^^^^^^ Could not find `simple_errors` in `nom`

error[E0433]: failed to resolve. Could not find `simple_errors` in `nom`
  --> /root/.cargo/registry/src/github.com-1ecc6299db9ec823/lettre-0.8.2/src/smtp/error.rs:98:16
   |
98 | impl From<nom::simple_errors::Err> for Error {
   |                ^^^^^^^^^^^^^ Could not find `simple_errors` in `nom`

error[E0433]: failed to resolve. Could not find `simple_errors` in `nom`
  --> /root/.cargo/registry/src/github.com-1ecc6299db9ec823/lettre-0.8.2/src/smtp/error.rs:99:23
   |
99 |     fn from(err: nom::simple_errors::Err) -> Error {
   |                       ^^^^^^^^^^^^^ Could not find `simple_errors` in `nom`

error[E0119]: conflicting implementations of trait `std::convert::From<[type error]>` for type `smtp::error::Error`:
   --> /root/.cargo/registry/src/github.com-1ecc6299db9ec823/lettre-0.8.2/src/smtp/error.rs:104:1
    |
98  | impl From<nom::simple_errors::Err> for Error {
    | -------------------------------------------- first implementation here
...
104 | impl From<Response> for Error {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `smtp::error::Error`

error[E0119]: conflicting implementations of trait `std::convert::From<[type error]>` for type `smtp::error::Error`:
   --> /root/.cargo/registry/src/github.com-1ecc6299db9ec823/lettre-0.8.2/src/smtp/error.rs:114:1
    |
98  | impl From<nom::simple_errors::Err> for Error {
    | -------------------------------------------- first implementation here
...
114 | impl From<&'static str> for Error {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `smtp::error::Error`

error: aborting due to 6 previous errors

Some errors occurred: E0119, E0432, E0433.
For more information about an error, try `rustc --explain E0119`.
error: Could not compile `lettre`.
warning: build failed, waiting for other jobs to finish...
error: build failed

I'm trying to use this crate in a project I'm working on, and I can't get the examples to compile. They cause panics.

My code (the example code):

use lettre::transport::smtp::{SmtpTransport, SmtpTransportBuilder};
use lettre::email::EmailBuilder;
use lettre::transport::EmailTransport;

let email = EmailBuilder::new()
                    .to("root@localhost")
                    .from("user@localhost")
                    .body("Hello World!")
                    .subject("Hello")
                    .build()
                    .unwrap();

// Open a local connection on port 25
let mut mailer =
SmtpTransportBuilder::localhost().unwrap().build();
// Send the email
let result = mailer.send(email);

assert!(result.is_ok());

The error:

thread '<main>' panicked at 'assertion failed: result.is_ok()', main.rs:26
note: Run with `RUST_BACKTRACE=1` for a backtrace.
Process didn't exit successfully: `/path/to/code` (exit code: 101)

Is your feature request related to a problem? Please describe. I'd like to store attachments in a struct like this:

#[derive(Debug, Serialize)]
pub struct Attachment {
    pub filename: String,
    pub content_type: ContentType,
    pub body_raw: Vec<u8>,
}

but the problem is, that ContentType can't be serialized, unless I implement the trait on my own.

Describe the solution you'd like That the Serialize macro-derives (I don't really know what the correct name is) serializes the type ContentType automatically for me.

Describe alternatives you've considered Implementing the Serialize trait on my own.

Additional context I don't think that we need an additional context here.

I've used the example smtp-gmail.rs for the 10 alpha release.

Unfortunately although it builds fine on Windws10 and Linux(RH7.4) I'm getting strange errors. I'm looking to eventually replace some perl scripts one of which sends mail:

        my $owner = "Simon.Heffer\@cpy.com";
        my $smtp = Net::SMTP->new("smtp.cpy.com",
                        Timeout => 60);
        $smtp->mail("Simon.Heffer\@cpy.com");
        $smtp->to($owner);
        $smtp->data;
        $smtp->datasend("Subject:$subject");
        $smtp->datasend("\n");
        $smtp->datasend("To: $owner");
                $smtp->datasend("\n\n");
        $smtp->datasend("\n");
        $smtp->datasend("\n\n");
        $smtp->dataend;
        $smtp->quit;

I've plugged in the servername/addresses from here into your example but get (on LINUX): Could not send email: Err(Pool(Error(None)))

I've tried with and without creds (there are none above)

Any further debugging I can do?

Potential fix for #742, but not sure if we consider this breaking. See the discussion there for background.

This implementation is loosely based on hyper-rustls (also MIT): https://github.com/rustls/hyper-rustls/blob/21c4d3749c5bac74eb934c56f1f92d76e1b88554/src/config.rs#L27-L47

Tested on macOS connecting to GMail.

Describe the bug A clear and concise description of what the bug is.

thread 'tokio-runtime-worker' panicked at 'Could not send email: lettre::transport::smtp::Error { kind: Network, source: Custom { kind: InvalidData, error: CorruptMessage } }', src/email_service.rs:52:19

To Reproduce

pub fn send_email() -> Result<(), ServiceError> {
    
    let email = Message::builder()
        .from("NoBody <[email protected]>".parse().unwrap())
        .reply_to("Yuin <[email protected]>".parse().unwrap())
        .to("Hei <[email protected]>".parse().unwrap())
        .subject("Happy new year")
        .body(String::from("Be happy!"))
        .unwrap();

    let creds = Credentials::new("etherealusername".to_string(), "etherealpassword".to_string());

    // Open a remote connection to gmail
    let mailer = SmtpTransport::relay("smtp.ethereal.email")
        .unwrap()
        .timeout(Some(std::time::Duration::new(5, 100)))
        .port(587)
        .credentials(creds)
        .build();

    // Send the email
    match mailer.send(&email) {
        Ok(_) => Ok(()),
        Err(e) => panic!("Could not send email: {:?}", e),
    }
}

Expected behavior Email should be received on ethereal

Environment (please complete the following information):

• Lettre version - 0.10.1
• OS macos m1

Additional context Add any other context about the problem here.

Since #827 #832 and #838, I thought about improving the parsing using https://github.com/zesterer/chumsky. This lib helps to build solid parsers and to be as close as possible to what RFCs propose.

Here (in this draft PR) a preview of what it could look like, is it sth you would be interested in or not?

Describe the bug

Double quote not removed when parsing Mailbox from str.

To Reproduce

let mbox: Mailbox = "\"Quoted, name\" <[email protected]>".parse().unwrap();
assert_eq!(Some("Quoted, name".into()), mbox.name);

// thread 'xxx' panicked at 'assertion failed: `(left == right)`
//   left: `Some("Quoted, name")`,
//  right: `Some("\"Quoted, name\"")`'

Expected behavior

Quotes should be removed

Environment (please complete the following information):

• Lettre version v0.10.1
• OS Linux 5.10.111 #1-NixOS SMP Wed Apr 13 19:01:11 UTC 2022

I'm not sure what this API should look like, but I have tried my best to reuse most of the code.

Maybe it would be better to store LMTP as a config parameter and return multiple responses for plain SMTP too, instead of specializing on LMTP protocol using const generic?

I have tried implementing separate struct for LMTP protocol, wrapping SMTP, however it would be too much boilerplate to delegate every method except send to wrapped SMTP connection.

I also have tried to use sealed generic instead of boolean const, but this didn't go well too (But maybe this approach can be implemented, if I'll try harder?)

trait Protocol;
struct Smtp;
struct Lmtp;
impl Protocol for Smtp {}
impl Protocol for Lmtp {}

impl<P: Protocol> MtpConnection<P> {...}
impl MtpConnection<Smtp> {...}
impl MtpConnection<Lmtp> {...}

Fixes: https://github.com/lettre/lettre/issues/820

Is your feature request related to a problem? Please describe. Creating a multiparty alternative (html & plain text) is not as straightforward as it sounds. Apart from one example for alternative parts there isn't anything in the crate to support this functionality.

Describe the solution you'd like I have a working example with a struct that I'd like to propose in order to:

• have attached files to the email
• have attached files for the html (used with src="cid:context_id.png")
• add both plain and html representation to the email

Additional context Should improve greatly the API design by providing this helper/builder for emails.