jmap-mail-client

What it is

RFC 8621 JMAP for Mail client methods — typed bindings on top of jmap-base-client.

Typed JMAP client methods for JMAP Mail (RFC 8621). An extension trait on jmap-base-client::JmapClient that adds all 26 RFC 8621 method calls as typed async methods.

What it's for

Implements RFC 8621 method bindings (Email/get, Mailbox/get/set/changes, Thread/get, EmailSubmission/set, Identity/get, SearchSnippet/get, MDN/send, etc.) on top of jmap-base-client. This crate is the canonical template for every extension *-client crate in the workspace — chat, calendars, tasks, contacts, filenode, sharing, and metadata all mirror its module layout and method-shape conventions. Depends on jmap-base-client for transport and session, and on jmap-mail-types for the wire types.

How to use

use jmap_base_client::{BearerAuth, ClientConfig, JmapClient};
use jmap_mail_client::{JmapMailExt, EmailGetParams};
use jmap_types::Id;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let auth = BearerAuth::new("my-token")?;
    let client = JmapClient::new_plain(auth, "https://jmap.example.com", ClientConfig::default())?;

    // Fetch the session and bind it to a mail session client.
    let session = client.fetch_session().await?;
    let mail = client.with_mail_session(session);

    // Fetch two emails with body values inlined.
    let params = EmailGetParams {
        fetch_text_body_values: Some(true),
        ..Default::default()
    };
    let ids = [Id::new_validated("e1")?, Id::new_validated("e2")?];
    let resp: jmap_mail_client::GetResponse<jmap_mail_types::Email> =
        mail.email_get(Some(&ids), None, Some(params)).await?;

    for email in &resp.list {
        println!("{}: {:?}", email.id, email.subject);
    }
    Ok(())
}

Id parameters are typed &jmap_types::Id (or &[jmap_types::Id] for slices) to make invalid Ids unrepresentable. State tokens use &jmap_types::State. Construct Ids with Id::new_validated(s) to enforce RFC 8620 §1.2 syntax at the boundary, or with Id::from(s) when the value is known-valid (e.g. already came back from a server response).

After calling JmapMailExt::with_mail_session(session) the returned [SessionClient] carries the session and makes it available to all methods without requiring the caller to pass it again. Construct a new SessionClient after each fetch_session call — do not reuse a stale one across session state changes.

Registered methods

All 26 RFC 8621 method names are available as typed async methods on [SessionClient]:

Id and State here are jmap_types::Id and jmap_types::State.

EmailSubmissionSetParams

EmailSubmissionSetParams carries two method-level fields that are sent at the top level of the EmailSubmission/set request body, not inside a create or update object:

pub struct EmailSubmissionSetParams {
    /// Map of creation key → JSON Merge Patch to apply to the related Email
    /// if the submission is created successfully (RFC 8621 §7.5).
    ///
    /// Keys prefixed with "#" are result references to creation keys in the
    /// same `create` map.  Typical use: remove `$draft` keyword on success.
    pub on_success_update_email: Option<serde_json::Value>,

    /// Email IDs (or "#"-prefixed creation keys) to destroy if the submission
    /// succeeds (RFC 8621 §7.5).
    ///
    /// Typical use: destroy the draft email after successful delivery.
    pub on_success_destroy_email: Option<Vec<String>>,
}

Both fields are omitted from the JSON payload when None.

EmailGetParams

EmailGetParams controls which body content the server includes in an Email/get response (RFC 8621 §4.1.8). All fields default to None (server default):

pub struct EmailGetParams {
    /// Which body-part properties to return (overrides server default list).
    pub body_properties: Option<Vec<String>>,

    /// If true, inline decoded values for text/plain body parts.
    pub fetch_text_body_values: Option<bool>,

    /// If true, inline decoded values for text/html body parts.
    pub fetch_html_body_values: Option<bool>,

    /// If true, inline decoded values for all body parts.
    pub fetch_all_body_values: Option<bool>,

    /// Maximum bytes of body value to return per part (0 or absent = no limit).
    pub max_body_value_bytes: Option<u64>,
}

Fields set to None are omitted from the request; the server uses its own defaults for omitted fields.

Response types

SetResponse<T> defaults to SetResponse<serde_json::Value> when no type parameter is given. Use SetResponse<Email> to get typed created/updated maps.

How it works

Every method on SessionClient follows the same six-step pipeline:

1. Validate arguments — defence-in-depth empty-state guards fire before any I/O, returning ClientError::InvalidArgument immediately. Id-shaped parameters are typed &Id / &[Id] and validated by construction (Id::new_validated); the production code does not re-validate Id syntax.
2. session_parts() — extracts (api_url, account_id) from the bound session; returns ClientError::InvalidSession if there is no primary account for urn:ietf:params:jmap:mail.
3. Build args JSON — constructs the serde_json::Value argument object, merging in any extra params structs by iterating their key-value pairs.
4. build_request(method, args, USING_MAIL) — wraps the single invocation into a JmapRequest with using = ["urn:ietf:params:jmap:core", "urn:ietf:params:jmap:mail"] and call ID "r1".
5. call_internal(api_url, &req) — delegates to jmap_base_client::JmapClient::call, which POSTs the request and returns a JmapResponse.
6. extract_response(&resp, CALL_ID) — finds the invocation for call ID "r1" in the response and deserializes it into the typed return value.

Examples

The crate ships one runnable example under examples/ demonstrating the end-to-end client flow:

• examples/mailbox_list.rs — fetch and print all mailboxes from a synthetic JMAP server (wiremock mock with a hand-written Mailbox/get response covering the common RFC 8621 §2.1 roles). Run: cargo run --example mailbox_list -p jmap-mail-client.

NOT FOR PRODUCTION — synthetic mock-server fixtures only, no auth, no TLS. Demonstrates the consume-side API.

Gotchas

• email_import requires a separately uploaded blob. RFC 8621 §4.8 Email/import operates on a previously uploaded raw RFC 5322 message; callers must upload the raw bytes via jmap_base_client::JmapClient's blob-upload API and pass the resulting blob_id to EmailImportInput. Likewise, email_parse operates on blobs already in the store.
• Partial Email/get via properties filtering breaks deserialization. Email has six required metadata fields (id, blob_id, thread_id, mailbox_ids, keywords, size, received_at). If the server omits any of these because of a properties filter, GetResponse<Email> will fail to deserialize. Use GetResponse<serde_json::Value> for partial-field responses.
• No streaming API for large email bodies. All body values returned by Email/get with fetch_*_body_values options are buffered in memory as part of the JMAP response. Very large messages should be downloaded via JmapClient::download_blob instead.
• Implicit Email/set from EmailSubmission/set. When EmailSubmissionSetParams::on_success_update_email or on_success_destroy_email is set, the server generates an implicit Email/set invocation and includes it in the response. extract_response extracts only the EmailSubmission/set result identified by call ID "r1". Callers that need to inspect the implicit Email/set result must call jmap_base_client::JmapClient::call directly and iterate JmapResponse::method_responses themselves.

Crate family

jmap-types
    ├── jmap-mail-types      Email, Mailbox, Thread, Identity, etc.
    │       └── jmap-mail-client  ← this crate
    └── jmap-base-client     transport, session, auth
            └── (also a dep of jmap-mail-client)

Path dependencies between crates use path = "../crate-jmap-*" and will remain that way until the family is published to crates.io.

References

• RFC 8621 — JMAP for Mail (method names, argument shapes, error conditions)
• RFC 8620 — JMAP Core (request/response envelope, /set and /query shapes, ResultReference, error types)
• RFC 5322 — Internet Message Format (message structure referenced by Email/import and Email/parse)