usesend-rs

Rust SDK for useSend — an open-source Resend alternative.

Installation

Add usesend to your project:

[dependencies]
usesend = "0.1"
tokio = { version = "1", features = ["macros", "rt-multi-thread"] }

Quick Start

#[tokio::main]
async fn main() -> usesend::ApiResult<()> {
    let client = usesend::UseSend::new("us_api_key");

    let resp = client.emails.build()
        .from("hello@example.com")
        .to("user@example.com")
        .subject("Hello from useSend!")
        .html("<h1>Welcome!</h1>")
        .send()
        .await?;

    println!("Sent: {}", resp.email_id);
    Ok(())
}

Features

Builder pattern — Fluent API for composing emails, contacts, campaigns, and more
Sub-service architecture — Organized access via client.emails, client.domains, client.contacts, etc.
Rate limiting — Built-in governor-based rate limiter with automatic 429 retry
Typed IDs — DomainId, EmailId, and other strongly-typed identifiers
Self-hosted support — Point to your own useSend instance with UseSend::with_base_url()
Environment variable — Read API key from USESEND_API_KEY via UseSend::from_env()

Usage

Send an Email

# async fn example() -> usesend::ApiResult<()> {
let client = usesend::UseSend::new("us_api_key");

client.emails.build()
    .from("noreply@example.com")
    .to("user@example.com")
    .subject("Order Confirmation")
    .html("<h1>Thanks for your order!</h1>")
    .cc("manager@example.com")
    .reply_to("support@example.com")
    .attachment("invoice.pdf", "<base64-content>")
    .send()
    .await?;
# Ok(())
# }

Manage Domains

# async fn example() -> usesend::ApiResult<()> {
let client = usesend::UseSend::new("us_api_key");

// Add a domain
let domain = client.domains.create("example.com", "us-east-1").await?;

// List all domains
let domains = client.domains.list().await?;

// Verify DNS records
let status = client.domains.verify(&domain.id).await?;
# Ok(())
# }

Contacts & Contact Books

# async fn example() -> usesend::ApiResult<()> {
let client = usesend::UseSend::new("us_api_key");

// Create a contact book
let book = client.contact_books.create("Newsletter Subscribers").await?;

// Add a contact
let contact = client.contacts.build(&book.id)
    .email("alice@example.com")
    .first_name("Alice")
    .last_name("Smith")
    .subscribed(true)
    .create()
    .await?;
# Ok(())
# }

Campaigns

# async fn example() -> usesend::ApiResult<()> {
let client = usesend::UseSend::new("us_api_key");

let campaign = client.campaigns.build()
    .name("Weekly Digest")
    .from("newsletter@example.com")
    .subject("This Week's Highlights")
    .contact_book_id("book_id")
    .html("<h1>Weekly Digest</h1>")
    .send_now(true)
    .create()
    .await?;
# Ok(())
# }

Self-hosted Instance

let client = usesend::UseSend::with_base_url(
    "us_api_key",
    "https://send.internal.company.com",
);

Environment Variable

// Reads USESEND_API_KEY from environment
let client = usesend::UseSend::from_env();

Feature Flags

Flag	Default	Description
`native-tls`	✅	Platform-native TLS (OpenSSL / Schannel / Secure Transport)
`rustls-tls`	❌	Pure-Rust TLS via rustls — no system dependency

[dependencies]
usesend = { version = "0.1", default-features = false, features = ["rustls-tls"] }

Crate Structure

Crate	Description
`usesend`	High-level SDK with builder pattern — use this
`usesend-api`	Low-level typed HTTP client and request/response models

Most users should depend on usesend. Use usesend-api directly only if you need raw access to the API types or want to build your own abstraction layer.

Minimum Supported Rust Version

The MSRV is 1.85 (Rust edition 2024).

Contributing

Contributions are welcome! Please feel free to open an issue or submit a pull request.

usesend-api 0.1.0