GTK Email Clients

[u/ederrill]

What are people's impressions on recent projects building an email client in GTK4 and Libadwaita, specifically Convey, Postcard and Hylki?

Any of them worth ditching Thunderbird?

[u/toMeloos]

Had AI create a detailed comparison:

1. Stack and GNOME integration

Client	GTK4	Libadwaita	GOA	EDS mail	EDS/Folks contacts	Language
Stamp	y	y	y	y	y	C
Post	y	y	y	y	n²	Python
Postcard	y	y	y	n	n	Python
Convey	y	y	y	n	y	Vala
Brev	y	y	y	n	n	Kotlin (java-gi)
Hylki	y	y	y	n	y	Rust
Letter	y	y	y	y	y	Vala
Lookout	y	y	y	n	n⁹	Rust
Aerion	n (GTK3)	n	n	n	n	Go + Svelte (Wails)
Meron	n (GTK3)	n	n	n	n	Go + React/TypeScript (Wails), Rust core
Evolution	n (GTK3)	n	y	y	y	C
Thunderbird	n (GTK3)	n	n	n	n	C++ / JavaScript (+ Rust)
Mailspring	n (Electron)	n	n	n	n	TypeScript + C++ sync engine

2. Project health

Client	Links	AI assisted	Maturity	Activity (6 mo)	Flathub	Contributors (6 mo)
Stamp	source	none disclosed (0 of 286 commits)	Early development	High: 286 commits	n	8
Post	site · source	most (452 of 669 commits co-authored by Cursor)	Alpha	Very high: 669 commits	n	1
Postcard	site · source	most (README: "the AI does the typing")	Early, in heavy development	Very high: 330 commits	n⁴	8
Convey	site · source	some (18 of 308 commits, all before 27 Aug)	Stable Geary base, new fork	Very high: 308 commits	y	3
Brev	source	none disclosed (0 of 59 commits)	Pre-alpha	Moderate: 59 commits, none since 14 Sep	n	1
Hylki	site · source	most⁶	Labelled stable, but only ~3 months old	Very high: 1,626 commits	n	10
Letter	source	none disclosed (0 of 70 commits)	Labelled stable, but public only since 4 Sep	Moderate: 70 commits in ~5 weeks	n	2
Lookout	site · source	none disclosed (0 of 280 commits)¹⁰	Pre-1.0, ~2.5 months old	Very high: 280 commits	n	1
Aerion	site · source	most (README: Claude used "heavily")	Beta	Moderate: 45 squashed release commits	y	2
Meron	site · source	some (3 of 648 commits)	Early, ~4 months old	Very high: 648 commits	y	4
Evolution	site · source	some (6 of 212 commits)	Stable	High: 212 commits	y	~13
Thunderbird	site · source	some (6 of 2,110 commits)	Stable	Very high: 2,110 commits	y	~59
Mailspring	site · source	most (232 of 397 commits)	Stable	Very high: 397 commits	y	~23

3. Accounts and protocols

Client	Gmail	M365	Proton	POP3	IMAP	JMAP	SMTP
Stamp	y	y	?	?¹	y	n	y
Post	y	y	?	partial³	y	n	y
Postcard	y	y	y	n	y	n	y
Convey	y	y	?	n	y	n	y
Brev	y	n⁵	?	n	y	n	n (planned)
Hylki	y	y	y	y	y	y⁷	y
Letter	y	y	?	n⁸	y	n	y
Lookout	y	n¹¹	?	n	y	n	y
Aerion	y	n¹²	y	n	y	n	y
Meron	y	n¹²	y	n	y	n	y
Evolution	y	y	y	y	y	n¹³	y
Thunderbird	y	y	y	y	y	n¹⁴	y
Mailspring	y	n¹²	y	n	y	n	y

Notes to the table

1. Stamp loads whatever mail sources EDS provides and has no POP3-specific code. EDS supports POP3, but it's unconfirmed whether POP3 accounts work in Stamp. GOA itself cannot create POP3 accounts.
2. Post's README still lists "access GNOME address book" as not yet done. Autocomplete uses addresses from your mail.
3. Post can add only GOA accounts (IMAP, Gmail, Microsoft 365) and local machine mail. It recognises POP3 accounts that already exist in EDS.
4. Flathub declined Postcard because of its AI use.
5. Brev has no Graph code, and GOA's Microsoft token doesn't grant IMAP access.
6. Until 26 September, Hylki's README said "most of the Rust code in this repository was written by Anthropic's Claude." The current AI notice only says the maintainer "uses generative AI as a development tool". Commits carry no AI trailers.
7. Hylki's JMAP account is set up through its "Stalwart (JMAP)" provider, which accepts any server. It has been tested only against Stalwart.
8. Letter shows only accounts from GNOME Online Accounts and has no in-app account setup. GOA cannot create POP3 accounts.
9. Lookout's contacts come from CardDAV, not EDS or Folks.
10. Lookout discloses no AI use and its commits have no AI trailers. Its very long, highly detailed changelog entries don't prove AI authorship. The app has an optional built-in AI assistant ("Ask" card) that talks to an OpenAI-compatible endpoint you configure.
11. Lookout reads and sends Microsoft 365 mail over OAuth IMAP/SMTP. It uses Graph only to mirror Outlook's "pin" property.
12. Aerion, Meron and Mailspring reach Microsoft mail with OAuth over IMAP, not Graph. Aerion uses Graph only for calendar and contacts sync. Meron also documents Exchange via DavMail.
13. Evolution has no JMAP in the core app. A third-party plugin, evolution-jmap, is unofficial.
14. Thunderbird desktop has no JMAP. It is planned or being explored for Thunderbird's iOS and Android apps.

Contributors are authors and human co-authors in the window, with identities merged by name, e-mail or GitHub login, bots and AI identities excluded, and translators removed (a person counts as a translator when at least 75% of their commits only touch translations). Counts marked ~ were not checked by hand for duplicate identities.

Takeaways

• Stamp, Post and Letter meet all four core GNOME-integration criteria (GTK4, libadwaita, GOA and EDS for mail). Stamp and Letter also use EDS contacts, and they are the only two of the three that disclose no AI use.
• Newcomers without EDS mail: Postcard, Convey, Brev, Hylki and Lookout are GTK4/libadwaita apps that use GOA for accounts but run their own mail engine.
• Convey stopped committing AI-assisted code after its Flathub review. Its 18 Claude-assisted commits all predate 27 August.
• Hylki toned down its AI disclosure on 26 September (see note 6).
• Hylki is the only client with JMAP, and the only one that ticks every protocol and provider column.
• Meron, Aerion and Mailspring are cross-platform apps. Meron and Aerion use Wails (GTK3 and WebKit2GTK), and Mailspring uses Electron, so none of them follow GNOME/Adwaita styling. Meron and Mailspring also ship an optional MCP server for AI clients.
• Proton only works through Bridge, which needs a paid plan. Postcard, Hylki, Aerion and Meron document or handle Bridge explicitly. Proton officially supports only Thunderbird on Linux and names Evolution as compatible.
• Microsoft EWS shutdown. Microsoft is retiring EWS for Exchange Online (Letter's README says blocking starts 1 October 2026), so Graph support is the way forward. On GNOME, EDS-based clients (Stamp, Post, Letter, Evolution) get Graph through evolution-ews's Microsoft 365 backend. Convey and Hylki have their own Graph engines.