Struct Message 

#[non_exhaustive]
pub struct Message {
    pub to: String,
    pub from: String,
    pub reply_to: Option<String>,
    pub subject: String,
    pub html: String,
    pub text: String,
    pub idempotency_key: Option<String>,
    pub tags: Vec<String>,
    pub headers: Vec<(String, String)>,
}

An outbound mail. text is always sent alongside html.

#[non_exhaustive]: build one with Message::new and the builder methods rather than a struct literal. A channel that has to set a header — RFC 8058 one-click unsubscribe, say — should not be a breaking change for every other caller, and before this it was.

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

to: String

from: String

reply_to: Option<String>

subject: String

html: String

text: String

idempotency_key: Option<String>

Passed through as an Idempotency-Key where the provider supports it.

tags: Vec<String>

headers: Vec<(String, String)>

Extra RFC 5322 headers, in order.

For headers the shape of Message does not name and should not: List-Unsubscribe and List-Unsubscribe-Post are the reason this exists, because Gmail and Yahoo have required one-click unsubscribe of bulk senders since 2024. An adapter that cannot send custom headers must say so rather than drop them silently.

Implementations

impl Message

pub fn new( to: impl Into<String>, from: impl Into<String>, subject: impl Into<String>, text: impl Into<String>, html: impl Into<String>, ) -> Self

The five parts every mail has. Everything else is a builder method.

pub fn reply_to(self, address: impl Into<String>) -> Self

Where a reply goes, when it is not from.

pub fn idempotency_key(self, key: impl Into<String>) -> Self

The key a provider that supports it uses to collapse a retry.

pub fn tags<I, T>(self, tags: I) -> Self

where I: IntoIterator<Item = T>, T: Into<String>,

Labels for the provider’s own reporting.

pub fn header(self, name: impl Into<String>, value: impl Into<String>) -> Self

One extra RFC 5322 header. Repeatable; order is preserved.

Trait Implementations

impl Clone for Message

fn clone(&self) -> Message

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Message

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.