emailengine
Headless email client
The Lens
By Erik Loyd, SaaS CEO and former COO/CFO of an AWS Premier Partner.
Updated Oct 2026
EmailEngine turns any mailbox into a REST API. Point it at Gmail, Microsoft 365 or any IMAP server and your app gets one API to read, send and sync mail, plus a webhook when a message lands. It's the self-hosted answer to Nylas. It is not free and not open source: the code is public, but running it past a 14-day trial takes a paid license.
Setup is EmailEngine plus Redis: Docker Compose, an install script for Ubuntu or Debian, or single binaries. Redis is the primary database here, not a cache: set noeviction, give it real memory, and skip Redis Cluster and ElastiCache, which aren't supported. The Nodemailer author builds it; releases ship every few days.
It costs $1,450 a year before VAT for unlimited instances and mailboxes, and you can serve your own customers from instances you manage. Nylas tiers cap connected accounts instead (25 on its $49/month plan). Solo: Nylas's free tier is easier. Small teams and up syncing many mailboxes: the flat fee wins.
The catch: stop paying and it stops working. License keys die 30 days after a subscription lapses, and the EULA bans touching the license check. Readable code isn't an exit plan.
Free vs Self-Hosted vs Paid
source availableFree: No free tier. Each install can activate a 14-day trial with full functionality, no sign-up or credit card. After that the core functionality stops until a license key is added. Source code is readable and modifiable for internal use only under the EmailEngine License (not an open source license).
Self-hosted: Self-hosted only, there is no hosted EmailEngine. Ships as a Docker image (postalsys/emailengine) with a Compose file that bundles a correctly configured Redis, an install.sh for Ubuntu/Debian that sets up Redis, a systemd service and Caddy for HTTPS, plus single binaries for macOS, Linux and Windows and an npm package. Redis is the primary data store, must use maxmemory-policy noeviction, and Redis Cluster and Amazon ElastiCache are not supported. Prometheus metrics at /metrics.
Paid: One subscription at $1,450/year (billed annually, VAT excluded) covers your company with unlimited instances, unlimited connected mailboxes, unlimited API calls and webhooks, unlimited license keys and all updates while active. You may serve your customers from instances you manage; they can't build their own services on top. Enterprise: perpetual license paid once, verified offline with no phone-home, invoice or wire payment, custom terms (contact sales). For comparison, Nylas (hosted) starts free for 5 connected accounts and charges $49/month for 25.
$1,450/year flat for unlimited mailboxes and instances after a 14-day trial, with no free tier. Cheap once you sync dozens of mailboxes, but let the subscription lapse and every instance stops 30 days later.
What to do by team size
- Solo
- 14-day trial to evaluate; at $1,450/year it only pays off if mailbox sync is core to your product, otherwise Nylas's free tier (5 accounts) is simpler
- Small team
- $1,450/year flat for unlimited mailboxes, fine if your app connects users' inboxes
- Medium team
- $1,450/year; the price is the same at 50 or 5,000 mailboxes, which is the whole pitch against per-account APIs
- Large team
- Enterprise perpetual license with offline verification and invoice billing, so an expired renewal can't take down instances on customer hardware
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Trust Signals
License: Proprietary EULA (source-available)
Source is public, but running it past a 14-day trial needs a paid license, and keys stop working 30 days after a subscription lapses.
Commercial use: ✗ Restricted
About
- Owner
- Postal Systems (Organization)
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