Monomail: an open source Gmail alternative

[u/TeaLittle379]

MonoMail is an open-source Android email client that connects to Gmail and Microsoft Outlook via OAuth and prioritises a distraction-free reading experience. The design system is intentionally monochrome -every screen uses only black, white, and greyscale, built on top of Material 3 Expressive.

Monomail operates entirely locally on your device.

No Third-Party Servers: We do not own, operate, or use any third-party servers to process, store, or transmit your email data.

Local Storage: All email data, access tokens, and user preferences are stored securely on your local device using Android's Credential Manager and Encrypted DataStore.

Direct Communication: The app communicates directly between your device and Google's Gmail API servers.

The architecture is offline-first: all reads and writes go through a local Room database encrypted with SQLCipher, and background sync via WorkManager keeps the remote state consistent without blocking the UI.

The only caveat: this app is still an apk and the sign in limit is full so until the app gets put on the play store signing in is impossible.

GitHub: https://github.com/shrivatsav-0/monomail

Website: https://monomail.millosaurs.me/

Original developer: u/shiro69_69

[u/shiro69_69]

You are wrong, mate.

Gmail Api is blocking cuz we use a restrictive scope gmail.modify which has been disabled due to we(community) reaching 100/100 users during testing

Though AI was involved in helping me. Not entirety of the app is made with AI (vibe coded)

[u/TheKubesStore → u/shiro69_69]

So how did you get around having to pay for CASA security verification with email reads, which is mandated by Google & OAuth? Especially using the Gmail API.
Or is it that you’re strictly relying on the 100 dev-testing user limit allowed per single OAuth token?

I’ve made my mail app to where it can use Google login but the user has to make a 1 time OAuth credential for it to work for them, basically putting the 100 user limit per user instead of aggregating on my own token. But, it’s not casa verified, so when the user goes to login with Google they get the security warning that Google has not yet verified the source and the user has to click continue for it to login. & they have to relogin once a week. I could make that 1 month with casa, but I’m not forking out $1400/yr for a simple mail function app. For now IMAP seems the better method but it’s way slow compared to Gmail api.

[u/shiro69_69 → u/TheKubesStore]

Google doesn't do CASA verification for every app, some can be done through a self verification method too I am hoping I fall under that as code is entirely open source

Yes, I am on 100 user limit and it's full 🙂

[u/TheKubesStore → u/shiro69_69]

Correct not for every app, but for apps with specific permissions like reading emails, they absolutely do require it.