7 Reasons to Consider Aerion: The Desktop Email Client That Surprised Me

If you juggle multiple email accounts daily, you know the struggle of switching between browser tabs. Desktop email clients offer a streamlined alternative, yet many users have drifted away from them. Recently, I decided to give desktop clients another try and stumbled upon a new open-source app that might just change your mind. Here are seven key things you need to know about Aerion, a lightweight, secure, and feature-rich email client that rekindled my enthusiasm.

1. Why Desktop Email Clients Still Matter

Desktop email clients centralize all your accounts in one place, avoiding the hassle of multiple browser tabs. They provide offline access, faster search, and better organization tools. Unlike web apps, they can handle large volumes of email without sluggish performance. For power users, dedicated clients offer advanced features like keyboard shortcuts, custom filters, and integrated calendars. While web interfaces have improved, desktop clients remain a productivity powerhouse. Aerion taps into this legacy, delivering a modern twist on a classic workflow.

2. My Journey from Thunderbird to Web Apps and Back

I first used Thunderbird years ago at a previous job—it did the job well enough. Over time, I switched to using Gmail and Outlook in the browser for the sake of convenience. But when I heard about Aerion, curiosity got the better of me. I decided to give desktop email clients another shot. The transition wasn’t just about nostalgia; it was about recapturing the efficiency and focus that a dedicated app can provide. Aerion promised a clean break from the bloat of older solutions, and I was eager to test that promise.

3. Introducing Aerion: A Fresh Open-Source Option

Aerion is an open-source desktop email client, sponsored by 3DF (which covers infrastructure and personnel costs). It draws inspiration from GNOME's Geary but aims for even lower resource usage. The app is built with Wails and Svelte, not Electron—so no memory hogging. This means a lightweight, responsive interface that won’t drag your system down. It’s still pre-release software, but its clean design and active development make it an exciting contender for Linux users and beyond.

4. Security First: CASA Tier 2 Certification

One standout feature is Aerion’s CASA Tier 2 certification, assessed by TAC Security (a Google-authorized assessor under the App Defense Alliance). This means the codebase has passed rigorous scans against OWASP ASVS standards. For a small indie project handling your email credentials, this independent audit offers immense peace of mind. It demonstrates a strong commitment to security that many larger clients lack.

5. Feature Set: Essentials Done Right

Aerion covers all the basics and then some: multiple account support, conversation threading, a WYSIWYG composer powered by TipTap, contact sync via CardDAV, Google, and Microsoft, multiple color themes, and keyboard navigation with vim-style shortcuts. These features help you stay productive without unnecessary clutter. The composer is intuitive, and threading makes long email chains easy to follow. For anyone who values efficiency, this arsenal is more than adequate.

6. Compatibility with Major Email Providers

Aerion works with Gmail, Microsoft 365/Outlook, Proton Mail (via the paywalled Proton Bridge), iCloud Mail, GMX Mail, and generic IMAP/SMTP. It also lists Yahoo, Fastmail, Zoho Mail, AOL Mail, and Mail.com, though these are currently untested. The inclusion of Proton Mail (albeit with a caveat) broadens its appeal to privacy-conscious users. Setup via OAuth is smooth for Gmail and Outlook, making it easy to get started.

7. Setup Experience: Smooth but with a Pitfall

Adding my Gmail account was surprisingly easy—Aerion redirected me to the browser for OAuth, and after granting permissions, I was back in the app, authenticated. However, there’s a nasty bug: if you accidentally click outside the “Add Email Account” window while it’s open, the whole window closes silently, discarding your progress without warning. It’s a frustrating hiccup that the developers should address before the stable release. Despite this, the core experience feels polished.

Aerion is still a work in progress, but its lightweight design, strong security credentials, and thoughtful features make it a desktop email client worth watching. If you're tired of bloated alternatives or the constant tab-switching of web apps, give Aerion a try—it might just deliver the experience you've been missing.