How to list Yahoo email threads

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Yahoo Mail doesn’t have a native threading API or a concept of conversation grouping at the protocol level. Under the hood, Nylas connects to Yahoo over IMAP and constructs threads by analyzing message headers. The result is a conversation view that works through the same Threads API you’d use for Gmail or Outlook.

This guide covers listing threads from Yahoo accounts, including how Nylas builds threads without native provider support, the 90-day message cache, and what to expect from thread grouping accuracy.

Why use Nylas for threads instead of IMAP directly?

Yahoo’s only developer-facing email interface is raw IMAP, and IMAP has no built-in concept of threads or conversations. To build a conversation view yourself, you’d need to parse In-Reply-To and References headers from every message, group them by conversation chain, handle subject-line variations, and maintain your own thread index. On top of that, Yahoo requires a signed Commercial Access Agreement before you can get API credentials.

Nylas handles all of this. The Threads API returns pre-grouped conversations with participant lists, read state, and the latest message content. Your code works across Yahoo, Gmail, Outlook, and every other provider without modification.

Before you begin

You’ll need:

• A Nylas application with a valid API key
• A grant for a Yahoo Mail account
• A Yahoo OAuth connector configured with your Yahoo app credentials (see Yahoo authentication guide)

New to Nylas? Start with the quickstart guide to set up your app and connect a test account before continuing here.

Yahoo OAuth setup

Yahoo requires a few extra steps compared to Google or Microsoft. You’ll need to:

1. Request API access by submitting a Yahoo Mail API Access form. Yahoo will send you a Commercial Access Agreement to sign. See the Yahoo authentication guide for the current process.
2. Create a Yahoo app by registering your application in the Yahoo Apps dashboard to get a client ID and secret.
3. Create a Yahoo connector in Nylas and configure it with your Yahoo client ID and secret.

If you’d rather skip the OAuth setup for testing, you can also authenticate Yahoo accounts using IMAP with an app password. OAuth is the better choice for production apps.

The full setup walkthrough is in the Yahoo authentication guide.

List threads

Make a List Threads request with the grant ID. By default, Nylas returns the most recent threads. These examples limit results to 5:

RequestResponseNode.js SDKPython SDKRuby SDKJava SDKKotlin SDK

curl --request GET \
  --url "https://api.us.nylas.com/v3/grants/<NYLAS_GRANT_ID>/threads?limit=5" \
  --header 'Accept: application/json, application/gzip' \
  --header 'Authorization: Bearer <NYLAS_API_KEY>' \
  --header 'Content-Type: application/json'

{
  "request_id": "1",
  "data": [
    {
      "starred": false,
      "unread": true,
      "folders": [
        "CATEGORY_PERSONAL",
        "INBOX",
        "UNREAD"
      ],
      "grant_id": "<NYLAS_GRANT_ID>",
      "id": "<THREAD_ID>",
      "object": "thread",
      "latest_draft_or_message": {
        "starred": false,
        "unread": true,
        "folders": [
          "UNREAD",
          "CATEGORY_PERSONAL",
          "INBOX"
        ],
        "grant_id": "<NYLAS_GRANT_ID>",
        "date": 1707836711,
        "from": [{
          "name": "Nyla",
          "email": "[email protected]"
        }],
        "id": "<MESSAGE_ID>",
        "object": "message",
        "snippet": "Send Email with Nylas APIs",
        "subject": "Learn how to Send Email with Nylas APIs",
        "thread_id": "<THREAD_ID>",
        "to": [{
          "email": "[email protected]"
        }],
        "created_at": 1707836711,
        "body": "Learn how to send emails using the Nylas APIs!"
      },
      "has_attachments": false,
      "has_drafts": false,
      "earliest_message_date": 1707836711,
      "latest_message_received_date": 1707836711,
      "participants": [{
        "email": "[email protected]"
      }],
      "snippet": "Send Email with Nylas APIs",
      "subject": "Learn how to Send Email with Nylas APIs",
      "message_ids": [
          "<MESSAGE_ID>"
      ]
    }
  ],
  "next_cursor": "123"
}

import 'dotenv/config'
import Nylas from 'nylas'

const NylasConfig = {
  apiKey: process.env.NYLAS_API_KEY,
  apiUri: process.env.NYLAS_API_URI,
}

const nylas = new Nylas(NylasConfig)

async function fetchRecentThreads() {
  try {
    const identifier = process.env.NYLAS_GRANT_ID
    const threads = await nylas.threads.list({
      identifier:identifier,
      queryParams: {
        limit: 5,
      }
    })

    console.log('Recent Threads:', threads)
  } catch (error) {
    console.error('Error fetching threads:', error)
  }
}

fetchRecentThreads()

from dotenv import load_dotenv
load_dotenv()

import os
import sys
from nylas import Client

nylas = Client(
    os.environ.get('NYLAS_API_KEY'),
    os.environ.get('NYLAS_API_URI')
)

grant_id = os.environ.get("NYLAS_GRANT_ID")

threads = nylas.threads.list(
  grant_id,
  query_params={
    "limit": 5
  }
)

print(threads)

require 'nylas'

nylas = Nylas::Client.new(api_key: '<NYLAS_API_KEY>')
query_params = { limit: 5 }
threads, _ = nylas.threads.list(identifier: '<NYLAS_GRANT_ID>', query_params: query_params)

threads.each {|thread|
  puts "#{thread[:subject]} | Participants: #{thread[:participants].map { |p| p[:email] }.join(', ')}"
}

import com.nylas.NylasClient;
import com.nylas.models.*;
import com.nylas.models.Thread;
import java.util.List;

public class ListThreads {
  public static void main(String[] args) throws NylasSdkTimeoutError, NylasApiError {
    NylasClient nylas = new NylasClient.Builder("<NYLAS_API_KEY>").build();
    ListThreadsQueryParams queryParams = new ListThreadsQueryParams.Builder().limit(5).build();
    ListResponse<Thread> threads = nylas.threads().list("<NYLAS_GRANT_ID>", queryParams);

    for(Thread thread : threads.getData()) {
      System.out.println(thread.getSubject());
    }
  }
}

import com.nylas.NylasClient
import com.nylas.models.*

fun main(args: Array<String>) {
    val nylas = NylasClient(apiKey = "<NYLAS_API_KEY>")
    val queryParams = ListThreadsQueryParams(limit = 5)
    val threads = nylas.threads().list("<NYLAS_GRANT_ID>", queryParams).data

    for (thread in threads) {
        println(thread.subject)
    }
}

The response includes a latest_draft_or_message object with the most recent message’s content. The same code works for Google, Microsoft, and IMAP accounts.

Filter threads

You can narrow results with query parameters. Here’s what works with Yahoo accounts:

Parameter	What it does	Example
subject	Match on subject line	?subject=Weekly standup
from	Filter by sender	[email protected]
to	Filter by recipient	[email protected]
unread	Unread only	?unread=true
in	Filter by folder or label ID	?in=INBOX
received_after	After a Unix timestamp	?received_after=1706000000
received_before	Before a Unix timestamp	?received_before=1706100000
has_attachment	Only results with attachments	?has_attachment=true

Here’s how to combine filters. This pulls threads with unread messages from a specific sender:

curlNode.js SDKPython SDK

curl --request GET \
  --url "https://api.us.nylas.com/v3/grants/<NYLAS_GRANT_ID>/[email protected]&unread=true&limit=10" \
  --header 'Accept: application/json' \
  --header 'Authorization: Bearer <NYLAS_API_KEY>'

const threads = await nylas.threads.list({
  identifier: grantId,
  queryParams: {
    from: "[email protected]",
    unread: true,
    limit: 10,
  },
});

threads = nylas.threads.list(
    grant_id,
    query_params={
        "from": "[email protected]",
        "unread": True,
        "limit": 10,
    }
)

Search with search_query_native

Yahoo supports the search_query_native parameter for IMAP-style search. Unlike Google and Microsoft, Yahoo lets you combine search_query_native with any other query parameter, not just in, limit, and page_token.

curlNode.js SDKPython SDK

curl --request GET \
  --url "https://api.us.nylas.com/v3/grants/<NYLAS_GRANT_ID>/threads?search_query_native=subject:invoice&limit=10" \
  --header 'Accept: application/json' \
  --header 'Authorization: Bearer <NYLAS_API_KEY>'

const threads = await nylas.threads.list({
  identifier: grantId,
  queryParams: {
    searchQueryNative: "subject:invoice",
    limit: 10,
  },
});

threads = nylas.threads.list(
    grant_id,
    query_params={
        "search_query_native": "subject:invoice",
        "limit": 10,
    }
)

Yahoo’s IMAP search doesn’t support NOT syntax. If you use a negation query, the results may still contain threads you intended to exclude. Filter those out in your application code instead.

See the search best practices guide for more on search_query_native across providers.

Things to know about Yahoo threads

Yahoo is IMAP-based with no native threading concept, which means threads behave differently from Google and Microsoft in several ways.

Threading is constructed, not native

Yahoo doesn’t assign a thread_id or ConversationId to messages. Nylas builds threads by analyzing In-Reply-To and References headers on each message, combined with subject-line matching. This works well for straightforward reply chains but is less precise than Gmail’s native threading.

A few scenarios where you might see differences compared to Gmail:

• Forwarded messages may or may not be grouped with the original thread, depending on whether the email client preserved the References header
• Subject-line edits can cause a message to split into a separate thread
• Messages without proper headers (from older or misconfigured email clients) might not group correctly

For most typical email conversations, the threading is accurate. Just be aware that edge cases exist.

The 90-day message cache affects threads

Nylas maintains a rolling cache of messages from the last 90 days for IMAP-based providers. Threads are built from cached messages, so conversations that span beyond 90 days may appear incomplete. The message_ids array only includes messages within the cache window.

To access older messages directly (not as threads), use query_imap=true on the Messages API. The Threads API does not support query_imap.

Thread metadata aggregation

Thread-level fields are computed from all cached messages in the conversation:

• unread is true if any message in the thread is unread
• starred is true if any message is starred
• has_attachments is true if any message has attachments
• participants is the union of all senders and recipients
• earliest_message_date reflects the oldest cached message, not necessarily the start of the conversation

Sync timing

Yahoo accounts rely on IMAP polling rather than push notifications. New messages typically appear within a few minutes, and threads update accordingly. For faster detection of new messages, use webhooks so Nylas notifies your server when changes sync.

Paginate through results

The Threads API returns paginated responses. When there are more results, the response includes a next_cursor value. Pass it back as page_token to get the next page:

curlNode.js SDKPython SDK

curl --request GET \
  --url "https://api.us.nylas.com/v3/grants/<NYLAS_GRANT_ID>/threads?limit=10&page_token=<NEXT_CURSOR>" \
  --header 'Accept: application/json' \
  --header 'Authorization: Bearer <NYLAS_API_KEY>'

let pageCursor = undefined;

do {
  const result = await nylas.threads.list({
    identifier: grantId,
    queryParams: {
      limit: 10,
      pageToken: pageCursor,
    },
  });

  // Process result.data here

  pageCursor = result.nextCursor;
} while (pageCursor);

page_cursor = None

while True:
    query = {"limit": 10}
    if page_cursor:
        query["page_token"] = page_cursor

    result = nylas.threads.list(grant_id, query_params=query)

    # Process result.data here

    page_cursor = result.next_cursor
    if not page_cursor:
        break

Keep paginating until the response comes back without a next_cursor.

What’s next

• Threads API reference for full endpoint documentation and all available parameters
• Using the Threads API for thread concepts and additional operations
• Messages API reference to fetch individual message content from threads
• List Yahoo messages for message-level operations on Yahoo accounts
• Search best practices for advanced search with search_query_native across providers
• Webhooks for real-time notifications instead of polling
• Yahoo authentication guide for full Yahoo setup including OAuth and IMAP options