OneSignal Android SDK alternatives for AI agents.

Thunderbird for Android – Open Source Email App for Android (fka K-9 Mail)

Kalendar is no ordinary library — it’s the Elder Wand of calendar components, crafted for Compose (now with KMP support) sorcerers who demand both power and elegance. With the flick of your wrist (or a few lines of Kotlin), you conjure a magical, interactive calendar that bends to your will. With Kalendar, your app becomes as organized as Hermione

Fully featured, open source, privacy friendly email app for Android

Decentralized private messenger with chat-shared tools and games for Android

The classic email sending library for PHP

The open-source communication infrastructure for agents and products

:love_letter: A beautiful, fast and fully open source mail client for Mac, Windows and Linux.

Mail-in-a-Box helps individuals take back control of their email by defining a one-click, easy-to-deploy SMTP+everything else server: a mail server in a box.

BillionMail gives you open-source MailServer, NewsLetter, Email Marketing — fully self-hosted, dev-friendly, and free from monthly fees. Join the discord: https://discord.gg/asfXzBUhZr

💌 Build and send emails using React

MJML: the only framework that makes responsive-email easy

A Cloudflare-based email service | 基于 Cloudflare 的邮箱服务 | Cloudflare Email 邮箱 Mail

Experience email the way you want with Mail0 – the first open source email app that puts your privacy and safety first. Join the discord: https://mail0.link/discord

✉️ Send e-mails with Node.JS – easy as cake!

Low code web framework for real world applications, in Python and Javascript

🧑‍🚀 Authentication and authorization infrastructure for SaaS and AI apps, built on OIDC and OAuth 2.1 with multi-tenancy, SSO, and RBAC.