ChainMail vs Spark: Which is better for Gmail users?

Different philosophies, different trade-offs

Spark by Readdle is a well-designed email client available on macOS, Windows, iOS, and Android. It connects to Gmail, Outlook, Yahoo, iCloud, and IMAP providers through a unified inbox. Spark processes your email on its own cloud servers to power features like Smart Inbox, AI writing, and team collaboration.

ChainMail takes the opposite approach: it connects directly to Gmail via Google's official API, processes everything locally on your machine, and doesn't route your email through any intermediate servers. It does one thing — Gmail — and focuses on doing it well.

The core trade-off: Spark gives you more features and cross-platform sync, but your emails pass through Readdle's servers. ChainMail keeps everything local and private, but it's Gmail-only and Windows-only (for now).

Where ChainMail wins

Privacy: your email stays on your machine

This is the biggest difference. Spark routes your email through Readdle's cloud servers to power its Smart Inbox sorting, AI features, and cross-device sync. That means a third-party company has access to your email content. Spark's privacy policy acknowledges this, and it's been a concern in the privacy community since the app launched.

ChainMail fetches email directly from Google's servers to your local machine. No intermediate servers, no cloud processing, no third-party access. If you're privacy-conscious — or your company has data handling requirements — this matters.

Native Gmail API vs IMAP

Spark connects to Gmail via IMAP with OAuth authentication. That means Gmail labels get mapped to folders, Gmail search operators don't fully work, and some Gmail-specific features (categories, importance markers) get lost in translation.

ChainMail uses Google's Gmail API natively. Labels work as labels. The full Gmail search syntax works (from:boss has:attachment larger:5M). Read/unread state, stars, and categories sync accurately because ChainMail speaks Gmail's native protocol.

Non-threaded message view

Spark uses threaded conversations exclusively — similar to Gmail's web interface. If you prefer seeing every email as its own row (like classic Outlook), Spark doesn't offer that option.

ChainMail supports both threaded and non-threaded views. In non-threaded mode, every message is a separate row that you can sort by sender, subject, date, or size. For people who manage high-volume inboxes, this is a significant workflow difference.

AI drafting with your own API key

Both Spark and ChainMail offer AI-powered email drafting, but the implementation is fundamentally different. Spark's AI runs on Readdle's servers — your email content is sent to their infrastructure for processing.

ChainMail's AI drafting uses a bring-your-own-key model. You connect your own API key from OpenAI, Anthropic, Google Gemini, Mistral, or other providers. The AI request goes directly from your machine to the AI provider — ChainMail never sees the content.

Simpler pricing, no subscription trap

Spark's free tier is functional but limited. Spark +Mail (the full individual plan) costs $4.99/month. Spark for Teams starts at $7.99/user/month. These are recurring subscriptions with no lifetime option.

ChainMail starts at $1/month, $10/year, or $35 for a lifetime license. No team pricing tiers, no feature gating between plans — every plan gets every feature.

Where Spark wins

Cross-platform availability

Spark runs on macOS, Windows, iOS, and Android with seamless sync between devices. If you check email on your phone and your laptop, Spark gives you a consistent experience everywhere. ChainMail is currently Windows-only (Mac is planned).

Smart Inbox and priority sorting

Spark's Smart Inbox automatically sorts incoming email into categories: Personal, Notifications, Newsletters, and Pinned. It surfaces what it thinks matters most. This is a genuinely useful feature for people drowning in email. ChainMail doesn't have automatic priority sorting.

Team collaboration

Spark has built-in team features: shared drafts, email delegation, internal comments on threads, and shared inboxes. If your team collaborates on email, Spark's team tools are mature and well-designed. ChainMail is a single-user client with no team features.

Multi-provider unified inbox

Spark handles Gmail, Outlook, Yahoo, iCloud, and generic IMAP accounts in one unified inbox. ChainMail is Gmail-only. If you have email accounts across providers, Spark is the more flexible choice.

Feature	Spark	ChainMail
Gmail API integration	✕ IMAP + OAuth	✓ Native Gmail API
Gmail labels (true labels)	✕ Mapped as folders	✓
Gmail search operators	Limited (IMAP search)	✓ Full Gmail syntax
Non-threaded message view	✕ Threaded only	✓
AI email drafting	✓ Cloud-processed	✓ BYOK, local
Smart templates with variables	Basic templates	✓ Variables + attachments
Smart Inbox (auto-sort)	✓	✕
Team collaboration	✓ Shared drafts, delegation	✕
Multiple email providers	✓ Gmail, Outlook, IMAP	✕ Gmail only
Platforms	macOS, Windows, iOS, Android	Windows (Mac planned)
Privacy (no cloud processing)	✕ Routes through Readdle servers	✓ Local-first, no intermediary
Price (individual)	$4.99/mo (Spark +Mail)	$1/mo
Lifetime license	✕ Subscription only	✓ $35
Dark mode	✓	✓

Who should pick ChainMail?

• Privacy-first users — if you don't want your email content routed through a third-party's cloud servers, ChainMail's local-first architecture is the clear choice
• Gmail-only users — ChainMail's native Gmail API gives you better label support, search, and sync than Spark's IMAP connection
• People who prefer non-threaded email — ChainMail lets you view every message as its own row; Spark forces threaded conversations
• Budget-conscious users — $1/mo or $35 lifetime vs $4.99/mo with no lifetime option
• Users who want private AI drafting — bring your own API key, no data sent to Readdle

Who should stick with Spark?

• Cross-platform users — if you need the same email client on Mac, Windows, iPhone, and Android
• Teams — if you need shared drafts, email delegation, and collaborative features
• Multi-provider users — if you manage Gmail + Outlook + Yahoo in one inbox
• People who love Smart Inbox — Spark's automatic priority sorting is genuinely useful for high-volume inboxes