wangamail-rs

Send email on behalf of a Microsoft tenant using Microsoft Graph API and app registration credentials (OAuth2 client credentials flow). Suitable for daemon apps and backend services. Part of the WangaMail family: wangamail-rs (Rust), wangamail-js (JavaScript), wangamail-py (Python), wangamail-net (.NET).

Documentation

• API docs: docs.rs/wangamail-rs (after publishing)
• Build locally: cargo doc --open in this crate

Requirements

• Rust 2021 edition
• An async runtime (e.g. tokio with full or rt-multi-thread + macros) in your binary when calling the async API

Azure setup

1. In Azure Portal, go to Microsoft Entra ID → App registrations → New registration.
2. Create a client secret under Certificates & secrets.
3. Under API permissions, add Microsoft Graph → Application permissions → Mail.Send, then Grant admin consent.
4. To send as a specific user, use that user’s Object (ID) or User principal name (e.g. user@yourtenant.onmicrosoft.com) as from_user. The app will send mail from that user’s mailbox (Exchange Online).

Usage

Add to Cargo.toml:

[dependencies]
wangamail-rs = "0.1"
tokio = { version = "1", features = ["full"] }

Example:

use wangamail_rs::{GraphMailClient, Message, MessageBody, BodyType, Recipient, SendMailRequest};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client = GraphMailClient::builder()
        .tenant_id(std::env::var("AZURE_TENANT_ID")?)
        .client_id(std::env::var("AZURE_CLIENT_ID")?)
        .client_secret(std::env::var("AZURE_CLIENT_SECRET")?)
        .build()?;

    let request = SendMailRequest::new(Message {
        subject: "Hello from Graph".to_string(),
        body: MessageBody {
            content_type: BodyType::Text,
            content: "This email was sent via Microsoft Graph.".to_string(),
        },
        to_recipients: vec![Recipient::new("recipient@example.com")],
        ..Default::default()
    });

    // Send as this user (must have a mailbox; app needs Mail.Send application permission)
    client
        .send_mail("user@yourtenant.onmicrosoft.com", request)
        .await?;

    Ok(())
}

Sovereign clouds

Override the token and Graph endpoints when using national clouds:

let client = GraphMailClient::builder()
    .tenant_id(tenant_id)
    .client_id(client_id)
    .client_secret(client_secret)
    .token_url("https://login.microsoftonline.us/your-tenant-id/oauth2/v2.0/token")
    .graph_base("https://graph.microsoft.us/v1.0")
    .build()?;

MCP (Model Context Protocol)

With the mcp feature, the crate exposes an MCP server so AI assistants (Cursor, Claude Desktop, etc.) can send email via the send_email tool.

Enable the feature

[dependencies]
wangamail-rs = { version = "0.1", features = ["mcp"] }

Run the MCP server (stdio)

Set AZURE_TENANT_ID, AZURE_CLIENT_ID, and AZURE_CLIENT_SECRET, then:

cargo run --example mcp_server --features mcp

The process speaks JSON-RPC over stdin/stdout. Configure your AI client to run this command as an MCP server (e.g. in Cursor MCP settings or Claude Desktop claude_desktop_config.json).

Tool: send_email

• from_user – User id or userPrincipalName to send as (e.g. user@tenant.onmicrosoft.com).
• to – List of recipient email addresses.
• subject – Subject line.
• body – Plain text or HTML body.
• body_type – "text" or "html" (default "text").
• cc, bcc – Optional lists of addresses.

Use from code

use wangamail_rs::mcp::WangaMailMcpServer;

// From env (AZURE_TENANT_ID, AZURE_CLIENT_ID, AZURE_CLIENT_SECRET)
let server = WangaMailMcpServer::from_env()?;

// Or with an existing client
let server = WangaMailMcpServer::new(client);

// Run over stdio (for subprocess use)
server.run_stdio().await?;

CI/CD

• Pull requests: Format (cargo fmt --check), lint (clippy), check, test.
• Push to main: Bump patch version, build, publish to crates.io, create a GitHub release.

To enable publish to crates.io, add a repository secret:

• CARGO_REGISTRY_TOKEN – crates.io API token with publish scope (crates.io/settings/tokens).

License

MIT OR Apache-2.0