### Install rustls-graviola crypto provider

Source: https://docs.rs/lettre/latest/index.html

Example of installing a custom rustls crypto provider, specifically rustls-graviola. Ensure the provider is installed before using lettre. Refer to the provider's documentation for specific setup instructions.

```rust
rustls_graviola::default_provider()
    .install_default()
    .expect("Failed to install crypto provider");
```

--------------------------------

### Trim Start Example (Hebrew)

Source: https://docs.rs/lettre/latest/lettre/message/header/struct.HeaderName.html

Demonstrates trimming leading whitespace from a string containing Hebrew characters.

```rust
let s = "  עברית  ";
assert!(Some('ע') == s.trim_start().chars().next());
```

--------------------------------

### DKIM Signing Example

Source: https://docs.rs/lettre/latest/src/lettre/message/mod.rs.html

Demonstrates how to build an email message and prepare it for DKIM signing. This example includes setting sender, recipient, subject, content type, and body, then proceeds to sign it.

```rust
let mut message = Message::builder()
    .from("Alice <alice@example.org>".parse().unwrap())
    .reply_to("Bob <bob@example.org>".parse().unwrap())
    .to("Carla <carla@example.net>".parse().unwrap())
    .subject("Hello")
    .header(ContentType::TEXT_PLAIN)
    .body("Hi there, it's a test email, with utf-8 chars ë!\n\n\n".to_owned())
    .unwrap();
let key = "-----BEGIN RSA PRIVATE KEY-----
MIIEowIBAAKCAQEAt2gawjoybf0mAz0mSX0cq1ah5F9cPazZdCwLnFBhRufxaZB8
NLTdc9xfPIOK8l/xGrN7Nd63J4cTATqZukumczkA46O8YKHwa53pNT6NYwCNtDUL
eBu+7xUW18GmDzkIFkxGO2R5kkTeWPlKvKpEiicIMfl0OmyW/fI3AbtM7e/gmqQ4
kEYIO0mTjPT+jTgWE4JIi5KUTHudUBtfMKcSFyM2HkUOExl1c9+A4epjRFQwEXMA
hM5GrqZoOdUm4fIpvGpLIGIxFgHPpZYbyq6yJZzH3+5aKyCHrsHawPuPiCD45zsU
re31zCE6b6k1sDiiBR4CaRHnbL7hxFp0aNLOVQIDAQABAoIBAGMK3gBrKxaIcUGo"
```

--------------------------------

### Mailbox::new Example

Source: https://docs.rs/lettre/latest/lettre/message/struct.Mailbox.html

Provides an example of using the `Mailbox::new` constructor with `use` statements for Address and Mailbox. Requires the `builder` feature.

```rust
use lettre::{Address, message::Mailbox};

let address = Address::new("example", "email.com")?;
let mailbox = Mailbox::new(None, address);
```

--------------------------------

### Async Tokio 1.x Sendmail Transport Example

Source: https://docs.rs/lettre/latest/lettre/transport/sendmail/index.html

This example demonstrates asynchronous email sending using Sendmail with the Tokio 1.x runtime. It requires the 'sendmail-transport' feature.

```rust
use lettre::{
    AsyncSendmailTransport,
    AsyncTransport,
    Message,
    SendmailTransport,
    Tokio1Executor,
    message::header::ContentType,
};

let email = Message::builder()
    .from("NoBody <nobody@domain.tld>".parse()?)
    .reply_to("Yuin <yuin@domain.tld>".parse()?)
    .to("Hei <hei@domain.tld>".parse()?)
    .subject("Happy new year")
    .header(ContentType::TEXT_PLAIN)
    .body(String::from("Be happy!"))?;

let sender = AsyncSendmailTransport::<Tokio1Executor>::new();
sender.send(email).await?;

```

--------------------------------

### Example of trim_start_matches with a character slice

Source: https://docs.rs/lettre/latest/lettre/message/header/struct.HeaderName.html

Demonstrates how to use `trim_start_matches` with a slice of characters to remove leading characters.

```rust
let x: &[_] = &['1', '2'];
assert_eq!("12foo1bar12".trim_start_matches(x), "foo1bar12");
```

--------------------------------

### DKIM Signing Example

Source: https://docs.rs/lettre/latest/lettre/struct.Message.html

Demonstrates how to build an email message and sign it using DKIM. Requires the 'builder' and 'dkim' features.

```rust
use lettre::{
    Message,
    message::{
        dkim::{DkimConfig, DkimSigningAlgorithm, DkimSigningKey},
        header::ContentType,
    },
};

let mut message = Message::builder()
    .from("Alice <alice@example.org>".parse().unwrap())
    .reply_to("Bob <bob@example.org>".parse().unwrap())
    .to("Carla <carla@example.net>".parse().unwrap())
    .subject("Hello")
    .header(ContentType::TEXT_PLAIN)
    .body("Hi there, it's a test email, with utf-8 chars ë!\n\n\n".to_owned())
    .unwrap();
let key = "-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY----- as DkimSigningKey::new(
    key,
    DkimSigningAlgorithm::Rsa,
).unwrap();
message.sign(&DkimConfig::default_config(
    "dkimtest".to_owned(),
    "example.org".to_owned(),
    signing_key,
));
println!(
    "message: {}",
    std::str::from_utf8(&message.formatted()).unwrap()
);
```

--------------------------------

### Example of Creating a SinglePart

Source: https://docs.rs/lettre/latest/src/lettre/message/mimebody.rs.html

Demonstrates how to construct a `SinglePart` with a `ContentType` of `TEXT_PLAIN` and a Unicode string body using the `SinglePart::builder()`.

```rust
let part = SinglePart::builder()
    .header(header::ContentType::TEXT_PLAIN)
    .body(String::from("Текст письма в уникоде"));
```

--------------------------------

### Install Custom Rustls Crypto Provider

Source: https://docs.rs/lettre/latest/src/lettre/lib.rs.html

Demonstrates how to install a custom crypto provider for Rustls, such as rustls-graviola. This is necessary when the 'rustls-no-provider' feature is enabled.

```rust
# mod rustls_graviola {
#     pub struct FakeProvider;
#     impl FakeProvider {
#         pub fn install_default(self) -> Result<(), String> { Ok(()) }
#     }
#     pub fn default_provider() -> FakeProvider { FakeProvider }
# }
// Example using the `rustls-graviola` crypto provider crate.
// Refer to your provider's documentation for the correct setup.
rustls_graviola::default_provider()
    .install_default()
    .expect("Failed to install crypto provider");

```

--------------------------------

### StubTransport Example

Source: https://docs.rs/lettre/latest/src/lettre/transport/stub/mod.rs.html

Demonstrates how to create and use the StubTransport to send an email and assert the logged message. Requires the 'builder' feature.

```rust
use lettre::{
    Message,
    Transport,
    message::header::ContentType,
    transport::stub::StubTransport,
};

# use std::error::Error;
# fn try_main() -> Result<(), Box<dyn Error>> {
let email = Message::builder()
    .from("NoBody <nobody@domain.tld>".parse()?)
    .reply_to("Yuin <yuin@domain.tld>".parse()?)
    .to("Hei <hei@domain.tld>".parse()?)
    .subject("Happy new year")
    .header(ContentType::TEXT_PLAIN)
    .body(String::from("Be happy!"))?;

let mut sender = StubTransport::new_ok();
sender.send(&email)?;
assert_eq!(
    sender.messages(),
    vec![
        (email.envelope().clone(), String::from_utf8(email.formatted()).unwrap())
    ],
);
# Ok(())
# }
# try_main().unwrap();

```

--------------------------------

### Sync Sendmail Example

Source: https://docs.rs/lettre/latest/src/lettre/transport/sendmail/mod.rs.html

Demonstrates sending an email synchronously using the SendmailTransport. Ensure the 'sendmail-transport' and 'builder' features are enabled.

```rust
use lettre::{Message, SendmailTransport, Transport, message::header::ContentType};

let email = Message::builder()
    .from("NoBody <nobody@domain.tld>".parse()?)
    .reply_to("Yuin <yuin@domain.tld>".parse()?)
    .to("Hei <hei@domain.tld>".parse()?)
    .subject("Happy new year")
    .header(ContentType::TEXT_PLAIN)
    .body(String::from("Be happy!"))?;

let sender = SendmailTransport::new();
sender.send(&email)?;
```

--------------------------------

### Sync File Transport Example

Source: https://docs.rs/lettre/latest/src/lettre/transport/file/mod.rs.html

Demonstrates sending an email using the synchronous FileTransport, writing the message to the local temporary directory.

```rust
use std::error::Error;

#[cfg(all(feature = "file-transport", feature = "builder"))]
fn main() -> Result<(), Box<dyn Error>> {
use std::env::temp_dir;

use lettre::{FileTransport, Message, Transport, message::header::ContentType};

// Write to the local temp directory
let sender = FileTransport::new(temp_dir());
let email = Message::builder()
    .from("NoBody <nobody@domain.tld>".parse()?)
    .reply_to("Yuin <yuin@domain.tld>".parse()?)
    .to("Hei <hei@domain.tld>".parse()?)
    .subject("Happy new year")
    .header(ContentType::TEXT_PLAIN)
    .body(String::from("Be happy!"))?;

sender.send(&email)?;
Ok(())
}

#[cfg(not(all(feature = "file-transport", feature = "builder")))]
fn main() {}

```

--------------------------------

### starts_with()

Source: https://docs.rs/lettre/latest/lettre/message/header/struct.HeaderName.html

Checks if the string slice starts with a given pattern.

```APIDOC
## starts_with()

### Description
Returns `true` if the given pattern matches a prefix of this string slice, and `false` otherwise. The pattern can be a `&str`, `char`, a slice of `char`s, or a function or closure that determines if a character matches.

### Method
`starts_with(pat)`

### Parameters
- **pat**: The pattern to check for at the beginning of the string. Can be `&str`, `char`, `&[char]`, or a closure `Fn(char) -> bool`.

### Response
- `bool`: `true` if the string starts with the pattern, `false` otherwise.
```

--------------------------------

### Creating a Sender Header

Source: https://docs.rs/lettre/latest/lettre/message/header/struct.Sender.html

Example of how to create a Sender header using the header! macro with a Mailbox. This requires the 'builder' feature.

```rust
header::Sender("Mr. Sender <sender@example.com>".parse().unwrap())
```

--------------------------------

### Sync FileTransport Example

Source: https://docs.rs/lettre/latest/lettre/transport/file/index.html

Writes emails to the local temporary directory. Ensure the `file-transport` feature is enabled.

```rust
use std::env::temp_dir;

use lettre::{FileTransport, Message, Transport, message::header::ContentType};

// Write to the local temp directory
let sender = FileTransport::new(temp_dir());
let email = Message::builder()
    .from("NoBody <nobody@domain.tld>".parse()?)
    .reply_to("Yuin <yuin@domain.tld>".parse()?)
    .to("Hei <hei@domain.tld>".parse()?)
    .subject("Happy new year")
    .header(ContentType::TEXT_PLAIN)
    .body(String::from("Be happy!"))?;

sender.send(&email)?;


```

--------------------------------

### DKIM Signing Example

Source: https://docs.rs/lettre/latest/lettre/message/struct.Message.html

Demonstrates how to build an email message, sign it with DKIM using a provided private key, and then format it for SMTP. Requires `builder` and `dkim` features.

```rust
use lettre::{
    Message,
    message::{
        dkim::{DkimConfig, DkimSigningAlgorithm, DkimSigningKey},
        header::ContentType,
    },
};

let mut message = Message::builder()
    .from("Alice <alice@example.org>".parse().unwrap())
    .reply_to("Bob <bob@example.org>".parse().unwrap())
    .to("Carla <carla@example.net>".parse().unwrap())
    .subject("Hello")
    .header(ContentType::TEXT_PLAIN)
    .body("Hi there, it's a test email, with utf-8 chars ë!\n\n\n".to_owned())
    .unwrap();
let key = "-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----

```

--------------------------------

### Create an Address with validation

Source: https://docs.rs/lettre/latest/lettre/address/struct.Address.html

This example demonstrates creating an Address using the `new` method, which includes validation. It ensures the provided user and domain are in a valid format.

```rust
use lettre::Address;

let address = Address::new("user", "email.com")?;
let expected = "user@email.com".parse::<Address>()?;
assert_eq!(expected, address);
```

--------------------------------

### Slice Length Example

Source: https://docs.rs/lettre/latest/lettre/message/enum.MaybeString.html

Demonstrates how to get the number of elements in a slice. This is a fundamental operation for understanding the size of data structures.

```rust
let a = [1, 2, 3];
assert_eq!(a.len(), 3);
```

--------------------------------

### Trim ASCII Start Example

Source: https://docs.rs/lettre/latest/lettre/message/enum.MaybeString.html

Removes leading ASCII whitespace from a byte slice. Whitespace is defined by `u8::is_ascii_whitespace`, excluding the `\0x0B` byte.

```rust
assert_eq!(b" \t hello world\n".trim_ascii_start(), b"hello world\n");
assert_eq!(b"  ".trim_ascii_start(), b"");
assert_eq!(b"".trim_ascii_start(), b"");
```

--------------------------------

### Getting the index of an element reference

Source: https://docs.rs/lettre/latest/lettre/message/enum.MaybeString.html

Use `element_offset` to find the index of a given element reference within a slice. Returns `None` if the reference is not aligned to an element's start.

```Rust
let nums: &[u32] = &[1, 7, 1, 1];
let num = &nums[2];

assert_eq!(num, &1);
assert_eq!(nums.element_offset(num), Some(2));
```

```Rust
let arr: &[[u32; 2]] = &[[0, 1], [2, 3]];
let flat_arr: &[u32] = arr.as_flattened();

let ok_elm: &[u32; 2] = flat_arr[0..2].try_into().unwrap();
let weird_elm: &[u32; 2] = flat_arr[1..3].try_into().unwrap();

assert_eq!(ok_elm, &[0, 1]);
assert_eq!(weird_elm, &[1, 2]);

assert_eq!(arr.element_offset(ok_elm), Some(0)); // Points to element 0
assert_eq!(arr.element_offset(weird_elm), None); // Points between element 0 and 1
```

--------------------------------

### Example of connecting with Tokio1 and TLS

Source: https://docs.rs/lettre/latest/lettre/transport/smtp/client/struct.AsyncSmtpConnection.html

Demonstrates how to establish an SMTP connection using Tokio1, including specifying server details, timeout, client ID, TLS parameters, and local address.

```rust
let connection = AsyncSmtpConnection::connect_tokio1(
    ("example.com", 465),
    Some(Duration::from_secs(60)),
    &ClientId::default(),
    Some(TlsParameters::new("example.com".to_owned())?),
    None,
)
.await?;
```

--------------------------------

### Removing a prefix with strip_prefix

Source: https://docs.rs/lettre/latest/lettre/message/enum.MaybeString.html

Use `strip_prefix` to get a subslice with the prefix removed. Returns `None` if the slice does not start with the specified prefix. An empty prefix returns the original slice.

```rust
let v = &[10, 40, 30];
assert_eq!(v.strip_prefix(&[10]), Some(&[40, 30][..]));
assert_eq!(v.strip_prefix(&[10, 40]), Some(&[30][..]));
assert_eq!(v.strip_prefix(&[10, 40, 30]), Some(&[][..]));
assert_eq!(v.strip_prefix(&[50]), None);
assert_eq!(v.strip_prefix(&[10, 50]), None)
```

```rust
let prefix : &str = "he";
assert_eq!(b"hello".strip_prefix(prefix.as_bytes()),
           Some(b"llo".as_ref()))
```

--------------------------------

### Format HELP Command

Source: https://docs.rs/lettre/latest/src/lettre/transport/smtp/commands.rs.html

Demonstrates formatting the HELP command, both with and without a specific argument.

```rust
assert_eq!(format!("{}", Help::new(None)), "HELP\r\n");
```

```rust
assert_eq!(
            format!("{}", Help::new(Some("test".to_owned()))),
            "HELP test\r\n"
        );
```

--------------------------------

### Iterate slice chunks from the end

Source: https://docs.rs/lettre/latest/lettre/message/enum.MaybeString.html

Use `rchunks` to get an iterator over slices of a specified size, starting from the end. The last chunk may be smaller if the slice size is not divisible by `chunk_size`. Panics if `chunk_size` is zero.

```rust
let slice = ['l', 'o', 'r', 'e', 'm'];
let mut iter = slice.rchunks(2);
assert_eq!(iter.next().unwrap(), &['e', 'm']);
assert_eq!(iter.next().unwrap(), &['o', 'r']);
assert_eq!(iter.next().unwrap(), &['l']);
assert!(iter.next().is_none());
```

--------------------------------

### Start TLS Encryption

Source: https://docs.rs/lettre/latest/lettre/transport/smtp/client/struct.SmtpConnection.html

Initiates a TLS handshake to encrypt the connection. Requires TLS parameters and a client ID.

```rust
pub fn starttls(
    &mut self,
    tls_parameters: &TlsParameters,
    hello_name: &ClientId,
) -> Result<(), Error>
```

--------------------------------

### Trim Prefix from Slice (Nightly)

Source: https://docs.rs/lettre/latest/lettre/message/enum.MaybeString.html

Use the experimental `trim_prefix` method to get a subslice with the prefix removed. If the slice does not start with the prefix, the original slice is returned. Handles empty prefixes and prefixes equal to the entire slice.

```rust
#![feature(trim_prefix_suffix)]

let v = &[10, 40, 30];

// Prefix present - removes it
assert_eq!(v.trim_prefix(&[10]), &[40, 30][..]);
assert_eq!(v.trim_prefix(&[10, 40]), &[30][..]);
assert_eq!(v.trim_prefix(&[10, 40, 30]), &[][..]);

// Prefix absent - returns original slice
assert_eq!(v.trim_prefix(&[50]), &[10, 40, 30][..]);
assert_eq!(v.trim_prefix(&[10, 50]), &[10, 40, 30][..]);

let prefix : &str = "he";
assert_eq!(b"hello".trim_prefix(prefix.as_bytes()), b"llo".as_ref());
```

--------------------------------

### Example Email Content

Source: https://docs.rs/lettre/latest/src/lettre/transport/file/mod.rs.html

This is an example of the content of an email file generated by the FileTransport.

```eml
From: NoBody <nobody@domain.tld>
Reply-To: Yuin <yuin@domain.tld>
To: Hei <hei@domain.tld>
Subject: Happy new year
Content-Type: text/plain; charset=utf-8
Date: Tue, 18 Aug 2020 22:50:17 GMT

Be happy!

```

--------------------------------

### Example Envelope Content

Source: https://docs.rs/lettre/latest/src/lettre/transport/file/mod.rs.html

This is an example of the JSON content for the envelope when using the FileTransport with envelope support.

```json
{"forward_path":["hei@domain.tld"],"reverse_path":"nobody@domain.tld"}

```

--------------------------------

### Async Tokio 1.x File Transport Example

Source: https://docs.rs/lettre/latest/src/lettre/transport/file/mod.rs.html

Demonstrates asynchronous email sending using `AsyncFileTransport` with the Tokio 1.x runtime, writing messages to the local temporary directory.

```rust
use std::error::Error;

#[cfg(all(feature = "tokio1", feature = "file-transport", feature = "builder"))]
async fn run() -> Result<(), Box<dyn Error>> {
use std::env::temp_dir;

use lettre::{
    AsyncFileTransport, AsyncTransport, Message, Tokio1Executor, message::header::ContentType,
};

// Write to the local temp directory
let sender = AsyncFileTransport::<Tokio1Executor>::new(temp_dir());
let email = Message::builder()
    .from("NoBody <nobody@domain.tld>".parse()?)
    .reply_to("Yuin <yuin@domain.tld>".parse()?)
    .to("Hei <hei@domain.tld>".parse()?)
    .subject("Happy new year")
    .header(ContentType::TEXT_PLAIN)
    .body(String::from("Be happy!"))?;

sender.send(email).await?;
Ok(())
}

```

--------------------------------

### Create and Format Standard Attachment

Source: https://docs.rs/lettre/latest/src/lettre/message/attachment.rs.html

Demonstrates creating a standard email attachment with a filename and body content, then asserts its formatted output.

```rust
let part = super::Attachment::new(String::from("test.txt")).body(
            String::from("Hello world!"),
            ContentType::parse("text/plain").unwrap(),
        );
        assert_eq!(
            &String::from_utf8_lossy(&part.formatted()),
            concat!(
                "Content-Disposition: attachment; filename=\"test.txt\"
",
                "Content-Type: text/plain
",
                "Content-Transfer-Encoding: 7bit

",
                "Hello world!\r
"
            )
        );
```

--------------------------------

### Get a typed Header

Source: https://docs.rs/lettre/latest/lettre/message/header/struct.Headers.html

Use `get()` to retrieve a copy of a specific `Header` type from the `Headers` collection. Returns `None` if the header is not present.

```rust
pub fn get<H: Header>(&self) -> Option<H>
```

--------------------------------

### Get Pooled SMTP Connection

Source: https://docs.rs/lettre/latest/src/lettre/transport/smtp/pool/async_impl.rs.html

Retrieves a connection from the pool, either by reusing an existing one or creating a new one if the pool is empty. Handles broken connections by discarding them and attempting to get another.

```rust
pub(crate) async fn connection(self: &Arc<Self>) -> Result<PooledConnection<E>, Error> {
        loop {
            let conn = {
                let mut connections = self.connections.lock().await;
                let Some(connections) = connections.as_mut() else {
                    // The transport was shut down
                    return Err(error::transport_shutdown());
                };
                connections.pop()
            };

            match conn {
                Some(conn) => {
                    let mut conn = conn.unpark();

                    // TODO: handle the client try another connection if this one isn't good
                    if !conn.test_connected().await {
                        #[cfg(feature = "tracing")]
                        tracing::debug!("dropping a broken connection");

                        conn.abort().await;
                        continue;
                    }

                    #[cfg(feature = "tracing")]
                    tracing::debug!("reusing a pooled connection");

                    return Ok(PooledConnection::wrap(conn, Arc::clone(self)));
                }
                None => {
                    #[cfg(feature = "tracing")]
                    tracing::debug!("creating a new connection");

                    let conn = self.client.connection().await?;
                    return Ok(PooledConnection::wrap(conn, Arc::clone(self)));
                }
            }
        }
    }
```

--------------------------------

### Create Help Command

Source: https://docs.rs/lettre/latest/lettre/transport/smtp/commands/struct.Help.html

Creates an instance of the HELP command, optionally with an argument. This function is part of the `Help` struct's implementation.

```rust
pub fn new(argument: Option<String>) -> Help
```

--------------------------------

### Any::type_id

Source: https://docs.rs/lettre/latest/lettre/transport/smtp/struct.SmtpTransportBuilder.html

Gets the `TypeId` of the SmtpTransportBuilder.

```APIDOC
## fn type_id(&self) -> TypeId

### Description
Gets the `TypeId` of `self`.

### Method
type_id

### Returns
TypeId - The unique identifier for the type of `self`.
```

--------------------------------

### AsyncSmtpConnection::server_info

Source: https://docs.rs/lettre/latest/lettre/transport/smtp/client/struct.AsyncSmtpConnection.html

Get information about the server.

```APIDOC
## AsyncSmtpConnection::server_info

### Description
Get information about the server.

### Method
`&self`

### Returns
`&ServerInfo` - Information about the SMTP server.
```

--------------------------------

### Build and Send Email via SMTP

Source: https://docs.rs/lettre/latest/lettre/transport/index.html

Demonstrates building an email using the `Message` API and sending it through an SMTP relay server. Requires SMTP credentials and server details. Ensure the `smtp` feature is enabled.

```rust
use lettre::{
    Message,
    SmtpTransport,
    Transport,
    message::header::ContentType,
    transport::smtp::authentication::Credentials,
};

let email = Message::builder()
    .from("NoBody <nobody@domain.tld>\".parse()?)
    .reply_to("Yuin <yuin@domain.tld>\".parse()?)
    .to("Hei <hei@domain.tld>\".parse()?)
    .subject("Happy new year")
    .header(ContentType::TEXT_PLAIN)
    .body(String::from("Be happy!"))?;

let creds = Credentials::new("smtp_username".to_owned(), "smtp_password".to_owned());

// Open a remote connection to the SMTP relay server
let mailer = SmtpTransport::relay("smtp.gmail.com")?
    .credentials(creds)
    .build();

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

--------------------------------

### T::type_id

Source: https://docs.rs/lettre/latest/lettre/message/struct.Message.html

Gets the TypeId of a type T.

```APIDOC
## T::type_id

### Description
Gets the `TypeId` of `self`.

### Signature
`fn type_id(&self) -> TypeId`
```

--------------------------------

### AsyncSmtpConnection::read_response

Source: https://docs.rs/lettre/latest/lettre/transport/smtp/client/struct.AsyncSmtpConnection.html

Gets the SMTP response from the server.

```APIDOC
## AsyncSmtpConnection::read_response

### Description
Gets the SMTP response from the server.

### Method
`&mut self`

### Returns
`Result<Response, Error>` - The server's response or an error.
```

--------------------------------

### Format RCPT TO Command

Source: https://docs.rs/lettre/latest/src/lettre/transport/smtp/commands.rs.html

Shows how to format the RCPT TO command, with and without parameters.

```rust
assert_eq!(
            format!("{}", Rcpt::new(email.clone(), vec![])),
            "RCPT TO:<test@example.com>\r\n"
        );
```

```rust
assert_eq!(
            format!("{}", Rcpt::new(email, vec![rcpt_parameter])),
            "RCPT TO:<test@example.com> TEST=value\r\n"
        );
```

--------------------------------

### Credentials Creation from Tuple

Source: https://docs.rs/lettre/latest/src/lettre/transport/smtp/authentication.rs.html

Demonstrates creating a `Credentials` struct from a tuple of string slices, providing a convenient way to initialize credentials.

```rust
assert_eq!(
            Credentials::new("alice".to_owned(), "wonderland".to_owned()),
            Credentials::from(("alice", "wonderland"))
        );
```

--------------------------------

### Address::domain

Source: https://docs.rs/lettre/latest/lettre/address/struct.Address.html

Gets the domain portion of the Address.

```APIDOC
## Address::domain

### Description
Gets the domain portion of the `Address`.

### Method
```
pub fn domain(&self) -> &str
```

### Returns
A string slice representing the domain part of the email address.

### Examples
```rust
use lettre::Address;

let address = Address::new("user", "email.com")?;
assert_eq!(address.domain(), "email.com");
```
```

--------------------------------

### Create and Add Mailbox to Mailboxes

Source: https://docs.rs/lettre/latest/src/lettre/message/mailbox/types.rs.html

Demonstrates creating a new Mailboxes instance and adding a Mailbox to it using the `with` method. This is useful for building a list of recipients.

```rust
use lettre::message::{Mailbox, Mailboxes};
use std::error::Error;

fn main() -> Result<(), Box<dyn Error>> {
    let address = Address::new("example", "email.com")?;
    let mut mailboxes = Mailboxes::new().with(Mailbox::new(None, address));
    Ok(())
}

```

--------------------------------

### Address::user

Source: https://docs.rs/lettre/latest/lettre/address/struct.Address.html

Gets the user portion of the Address.

```APIDOC
## Address::user

### Description
Gets the user portion of the `Address`.

### Method
```
pub fn user(&self) -> &str
```

### Returns
A string slice representing the user part of the email address.

### Examples
```rust
use lettre::Address;

let address = Address::new("user", "email.com")?;
assert_eq!(address.user(), "user");
```
```

--------------------------------

### PartialEq Implementation for Help

Source: https://docs.rs/lettre/latest/lettre/transport/smtp/commands/struct.Help.html

Tests for equality between two Help command instances. Used by the `==` operator.

```rust
fn eq(&self, other: &Help) -> bool
```

```rust
fn ne(&self, other: &Rhs) -> bool
```

--------------------------------

### Get Headers

Source: https://docs.rs/lettre/latest/src/lettre/message/mimebody.rs.html

Returns a reference to the headers of the multipart message.

```APIDOC
## headers

### Description
Get the headers from the multipart.

### Signature
pub fn headers(&self) -> &Headers
```

--------------------------------

### Format ServerInfo with Features

Source: https://docs.rs/lettre/latest/src/lettre/transport/smtp/extension.rs.html

Illustrates the string representation of ServerInfo, including cases with and without supported features.

```rust
assert_eq!(
            format!("{}",
                ServerInfo {
                    name: "name".to_owned(),
                    features: eightbitmime,
                }
            ),
            "name with {EightBitMime}".to_owned()
        );

        assert_eq!(
            format!("{}",
                ServerInfo {
                    name: "name".to_owned(),
                    features: empty,
                }
            ),
            "name with no supported features".to_owned()
        );

        assert_eq!(
            format!("{}",
                ServerInfo {
                    name: "name".to_owned(),
                    features: plain,
                }
            ),
            "name with {Authentication(Plain)}".to_owned()
        );
```

--------------------------------

### Format ClientId and Localhost

Source: https://docs.rs/lettre/latest/src/lettre/transport/smtp/extension.rs.html

Demonstrates the string formatting for ClientId and a localhost constant.

```rust
assert_eq!(
            format!("{}", ClientId::Domain("test".to_owned())),
            "test".to_owned()
        );
        assert_eq!(format!("{}", LOCALHOST_CLIENT), "[127.0.0.1]".to_owned());
```

--------------------------------

### strip_prefix

Source: https://docs.rs/lettre/latest/lettre/message/enum.MaybeString.html

Returns a subslice with the prefix removed. If the slice starts with `prefix`, returns the subslice after the prefix, wrapped in `Some`. If `prefix` is empty, simply returns the original slice. If `prefix` is equal to the original slice, returns an empty slice. If the slice does not start with `prefix`, returns `None`.

```APIDOC
## pub fn strip_prefix<P>(&self, prefix: &P) -> Option<&[T]>
where P: SlicePattern<Item = T> + ?Sized, T: PartialEq,

### Description
Returns a subslice with the prefix removed. If the slice starts with `prefix`, returns the subslice after the prefix, wrapped in `Some`. If `prefix` is empty, simply returns the original slice. If `prefix` is equal to the original slice, returns an empty slice. If the slice does not start with `prefix`, returns `None`.

### Parameters
#### Path Parameters
- **prefix** (&P) - Required - The prefix to remove.

### Examples
```rust
let v = &[10, 40, 30];
assert_eq!(v.strip_prefix(&[10]), Some(&[40, 30][..]));
assert_eq!(v.strip_prefix(&[10, 40]), Some(&[30][..]));
assert_eq!(v.strip_prefix(&[10, 40, 30]), Some(&[][..]));
assert_eq!(v.strip_prefix(&[50]), None);
assert_eq!(v.strip_prefix(&[10, 50]), None);
```
```

--------------------------------

### Create Mailbox from Address

Source: https://docs.rs/lettre/latest/lettre/message/struct.Mailbox.html

Demonstrates creating a Mailbox instance using an Address object and an optional name. Requires the `builder` feature.

```rust
let address = Address::new("example", "email.com")?;
let mailbox = Mailbox::new(None, address);
```

--------------------------------

### Reverse Splitting of a Slice by a Predicate

Source: https://docs.rs/lettre/latest/lettre/message/enum.MaybeString.html

Returns an iterator over subslices separated by elements that match a predicate, starting from the end of the slice and working backwards. The matched element is not included in the subslices. Handles edge cases like delimiters at the start or end, producing empty slices.

```rust
let slice = [11, 22, 33, 0, 44, 55];
let mut iter = slice.rsplit(|num| *num == 0);

assert_eq!(iter.next().unwrap(), &[44, 55]);
assert_eq!(iter.next().unwrap(), &[11, 22, 33]);
assert_eq!(iter.next(), None);
```

```rust
let v = &[0, 1, 1, 2, 3, 5, 8];
let mut it = v.rsplit(|n| *n % 2 == 0);
assert_eq!(it.next().unwrap(), &[]);
assert_eq!(it.next().unwrap(), &[3, 5]);
assert_eq!(it.next().unwrap(), &[1, 1]);
assert_eq!(it.next().unwrap(), &[]);
assert_eq!(it.next(), None);
```

--------------------------------

### SmtpConnection Usage

Source: https://docs.rs/lettre/latest/lettre/transport/smtp/client/index.html

Demonstrates how to establish an SMTP connection and send basic commands like MAIL, RCPT, DATA, MESSAGE, and QUIT.

```APIDOC
## SmtpConnection Usage

### Description

This example shows how to create an `SmtpConnection`, send a `Mail` command, add a `Rcpt` recipient, send the `Data` and `Message`, and finally close the connection with `Quit`.

### Method

Not applicable (SDK usage)

### Endpoint

Not applicable (SDK usage)

### Parameters

Not applicable (SDK usage)

### Request Example

```rust
use lettre::transport::smtp::{
    SMTP_PORT,
    client::SmtpConnection,
    commands::*,
    extension::ClientId,
};

let hello = ClientId::Domain("my_hostname".to_owned());
let mut client = SmtpConnection::connect(&("localhost", SMTP_PORT), None, &hello, None, None)?;
client.command(Mail::new(Some("user@example.com".parse()?), vec![]))?;
client.command(Rcpt::new("user@example.org".parse()?, vec![]))?;
client.command(Data)?;
client.message("Test email".as_bytes())?;
client.command(Quit)?;
```

### Response

Not applicable (SDK usage)
```

--------------------------------

### ServerInfo::get_auth_mechanism

Source: https://docs.rs/lettre/latest/lettre/transport/smtp/extension/struct.ServerInfo.html

Gets a compatible authentication mechanism from a provided list.

```APIDOC
### `pub fn get_auth_mechanism(&self, mechanisms: &[Mechanism]) -> Option<Mechanism>`

Gets a compatible mechanism from a list.
```

--------------------------------

### Upgrade to TLS Connection

Source: https://docs.rs/lettre/latest/src/lettre/transport/smtp/client/connection.rs.html

Handles the STARTTLS command to upgrade the connection to TLS. Requires a TLS feature to be enabled. If STARTTLS is not supported by the server, it returns an error.

```rust
if self.server_info.supports_feature(Extension::StartTls) {
            #[cfg(any(feature = "native-tls", feature = "rustls", feature = "boring-tls"))]
            {
                try_smtp!(self.command(Starttls), self);
                self.stream.get_mut().upgrade_tls(tls_parameters)?;
                #[cfg(feature = "tracing")]
                tracing::debug!("connection encrypted");
                // Send EHLO again
                try_smtp!(self.ehlo(hello_name), self);
                Ok(())
            }
            #[cfg(not(any(feature = "native-tls", feature = "rustls", feature = "boring-tls")))]
            // This should never happen as `Tls` can only be created when a TLS library is enabled
            unreachable!("TLS support required but not supported");
        } else {
            Err(error::client("STARTTLS is not supported on this server"))
        }
```

--------------------------------

### Implement Any for T

Source: https://docs.rs/lettre/latest/lettre/transport/smtp/commands/struct.Noop.html

Gets the TypeId of a type, useful for runtime type identification.

```rust
fn type_id(&self) -> TypeId

```

--------------------------------

### Get Body Encoding Type

Source: https://docs.rs/lettre/latest/lettre/message/struct.Body.html

Returns the ContentTransferEncoding used for this body.

```rust
pub fn encoding(&self) -> ContentTransferEncoding
```

--------------------------------

### Async Tokio 1.x Sendmail Example

Source: https://docs.rs/lettre/latest/src/lettre/transport/sendmail/mod.rs.html

Shows how to send an email asynchronously using SendmailTransport with the Tokio 1.x runtime. Requires 'tokio1', 'sendmail-transport', and 'builder' features.

```rust
use lettre::{
    AsyncSendmailTransport, AsyncTransport, Message, SendmailTransport, Tokio1Executor,
    message::header::ContentType,
};

let email = Message::builder()
    .from("NoBody <nobody@domain.tld>".parse()?)
    .reply_to("Yuin <yuin@domain.tld>".parse()?)
    .to("Hei <hei@domain.tld>".parse()?)
    .subject("Happy new year")
    .header(ContentType::TEXT_PLAIN)
    .body(String::from("Be happy!"))?;

let sender = AsyncSendmailTransport::<Tokio1Executor>::new();
sender.send(email).await?;
```