# Filo Is Now Officially Google CASA Tier 3 Verified

After months of rigorous third‑party testing, Filo has officially passed Google's highest‑level [Cloud Application Security Assessment (CASA)](https://appdefensealliance.dev/casa) Tier 3.

Because Filo is an independent app (not a Chrome extension in the Web Store), you won't see a public badge floating around — but you can take our word for it: we cleared every single Tier 3 control.

## A Quick Refresher: What is CASA?

CASA stands for Cloud Application Security Assessment — Google Workspace's independent audit program for third‑party apps that connect to Gmail, Drive, Calendar, and the rest of the Google stack. It has three levels:

If Tier 1 is a driver's‑license eye test, Tier 3 is the race‑track stress test: every safety system is inspected at high speed by specialists who don't work for us.

## Why Tier 3 is rare — especially for email apps

- **High stakes** — Email is a gold mine for attackers. Google only recommends Tier 3 for apps that handle sensitive data at scale.
- **No shortcuts** — The lab must verify every security control — encryption, access controls, logging, incident response, data‑retention rules — before signing off.
- **Annual renewal** — Pass once, celebrate briefly, then do it all over again in twelve months.

Filo joins a short list of inbox tools that have met that bar.

## What the auditors looked for — and what they found

All tests performed by an independent, Google-authorized security lab as part of CASA Tier 3.

## Turning audit jargon into everyday peace of mind

**"Do you keep my emails on your servers?"**  
**Never.** Auditors validated that message bodies, attachments, and even cached snippets live only on your phone or desktop. We see headers for routing; that's it.

**"Can your AI models 'remember' what I wrote?"**  
**No.** Models run stateless requests: they process, respond, and forget. The lab traced every call → auto‑delete timestamp.

**"Is my data encrypted the whole way?"**  
**Yes.** End‑to‑end TLS from Google to your device, plus device‑level AES storage. Keys rotate automatically; auditors reviewed the rotation logs.

**"What if I hit 'Delete Account' in the settings?"**  
**One tap triggers a cascade:** revoke OAuth tokens ➜ purge metadata ➜ wipe local cache. The independent auditors verified that this workflow leaves no residual data on Filo servers or in your Google account.

## Help Us Spread the Word ❤️

If you've ever hesitated to trust an AI inbox, we hope this blog — and the green shield behind it — earns a little of that trust back. Share this post, tell a friend who still forwards emails to themselves, or drop by our [Discord community](https://discord.gg/filomail).

Until the next milestone,

_The Filo Team — powered by ☕️ caffeine, curiosity, and now, CASA Tier 3 confidence._