Environment Variables

Security & Database

Variable	Required	Description	Example
`BETTER_AUTH_SECRET`	Yes	Signing/encryption secret for sessions and for the secret-reveal key (HKDF-derived from it). Must be at least 32 characters. Generate with `openssl rand -base64 32`.	`s3cr3t...`
`DB_PASSWORD`	Yes	PostgreSQL database password. Used by the Docker Compose setup.	`changeme123`
`DATABASE_URL`	Yes	Full PostgreSQL connection string. Auto-configured in Docker.	`postgresql://sendly:password@postgres:5432/sendly`
`REDIS_URL`	Yes	Redis connection string.	`redis://redis:6379`
`PORT`	No	Port the API server listens on.	`8080` (default)

Set your subdomains here. The application automatically derives all internal and client-side URLs from these at container startup — you don't need to set *_URI or NEXT_PUBLIC_* variables manually.

Variable	Required	Description	Example
`API_DOMAIN`	Yes	Subdomain for the API server.	`api.yourdomain.com`
`DASHBOARD_DOMAIN`	Yes	Subdomain for the dashboard app.	`app.yourdomain.com`
`LANDING_DOMAIN`	Yes	Subdomain for the landing page.	`www.yourdomain.com`
`WIKI_DOMAIN`	Yes	Subdomain for the documentation site.	`docs.yourdomain.com`
`USE_HTTPS`	No	Set to `true` when running behind a TLS-terminating reverse proxy. Used to construct URLs with the correct protocol.	`false` (default)

AWS SES

Variable	Required	Description	Example
`AWS_SES_REGION`	Yes	AWS region where SES is configured.	`us-east-1`
`AWS_SES_ACCESS_KEY_ID`	Yes	AWS access key ID with SES send permissions.	`AKIA...`
`AWS_SES_SECRET_ACCESS_KEY`	Yes	AWS secret access key for SES.	`wJalr...`
`SES_CONFIGURATION_SET`	No	SES configuration set name used for open/click tracking.	`sendly-configuration-set` (default)
`SES_CONFIGURATION_SET_NO_TRACKING`	No	A second SES configuration set without tracking. When set, projects can toggle email tracking on/off. If omitted, the tracking toggle is hidden.	`sendly-no-tracking-configuration-set` (default)

Storage (Minio)

The bundled Docker setup includes Minio with defaults that work out of the box. Only change these when connecting to an external S3-compatible bucket.

Variable	Required	Description	Default
`MINIO_ROOT_USER`	No	Minio root username (Docker Compose only).	`sendly`
`MINIO_ROOT_PASSWORD`	No	Minio root password (Docker Compose only).	`sendlyminiopass`
`MINIO_API_PORT`	No	Port for the Minio API (Docker Compose only).	`9000`
`MINIO_CONSOLE_PORT`	No	Port for the Minio console UI (Docker Compose only).	`9001`
`S3_ENDPOINT`	No	S3 or Minio endpoint URL.	`http://minio:9000`
`S3_ACCESS_KEY_ID`	No	S3 or Minio access key.	—
`S3_ACCESS_KEY_SECRET`	No	S3 or Minio secret key.	—
`S3_BUCKET`	No	Bucket name for file uploads.	`uploads`
`S3_PUBLIC_URL`	No	Publicly accessible base URL for stored files.	—
`S3_FORCE_PATH_STYLE`	No	Use path-style URLs instead of virtual-hosted. Required for Minio.	`true`

SMTP Server

The optional SMTP relay lets you send emails through Sendly via the SMTP protocol.

Variable	Required	Description	Default
`SMTP_DOMAIN`	No	SMTP relay domain. Required when using Traefik's `acme.json` with multiple certificates so the correct cert can be selected.	`localhost`
`SMTP_ENABLED`	No	Explicitly enable SMTP features in the UI. Automatically enabled when `SMTP_DOMAIN` is set to a non-localhost value in production.	`false`
`PORT_SECURE`	No	SMTPS port (implicit TLS).	`465`
`PORT_SUBMISSION`	No	SMTP submission port (STARTTLS).	`587`
`MAX_RECIPIENTS`	No	Maximum number of recipients per email.	`5`

OAuth

Enables social login. Register an OAuth app with each provider and add the credentials here.

Variable	Required	Description
`GITHUB_OAUTH_CLIENT`	No	GitHub OAuth app client ID.
`GITHUB_OAUTH_SECRET`	No	GitHub OAuth app client secret.
`GOOGLE_OAUTH_CLIENT`	No	Google OAuth app client ID.
`GOOGLE_OAUTH_SECRET`	No	Google OAuth app client secret.

Stripe

All four are required, and there is no "billing disabled" mode. While they were optional the app derived a STRIPE_ENABLED flag from their presence, which made the monthly usage cap, the pre-send campaign billing check and usage metering into silent no-ops on any install that had not configured Stripe — enforcement became a function of how completely someone had filled in their environment. A missing value now fails boot instead.

There is no flat-monthly price. Checkout sells one metered line item, and STRIPE_PRICE_PRO_FLAT_MONTHLY (formerly STRIPE_PRICE_ONBOARDING) is a retired name that fails boot if it is still set.

| Variable | Required | Description | | -------------------------- | -------- | --------------------------------------------------------------------- | ------------------ | | STRIPE_SK | Yes | Stripe secret key. | | STRIPE_WEBHOOK_SECRET | Yes | Stripe webhook signing secret for verifying events. | | STRIPE_PRICE_EMAIL_USAGE | Yes | Stripe price ID for the metered, graduated pay-per-email usage price. | | STRIPE_METER_EVENT_NAME | Yes | Stripe meter event name. | emails (default) |

Platform Emails

When configured, Sendly will send email notifications to users for critical events (e.g. project disabled, billing limits reached). Without these, only ntfy notifications are sent.

Variable	Required	Description	Example
`SENDLY_PLATFORM_SEND_API_KEY`	Yes	API key Sendly sends its OWN platform mail with.	`pk_...`
`SENDLY_FROM_ADDRESS`	Yes	From address used for platform notification emails.	`noreply@yourdomain.com`

Notifications (ntfy)

Sendly bundles a self-hosted ntfy server for internal system notifications.

Variable	Required	Description	Default
`NTFY_PORT`	No	Port for the ntfy web UI (Docker Compose only).	`8080`
`NTFY_URL`	No	ntfy topic URL. Change this to use an external ntfy.sh server or your own instance.	`http://ntfy/sendly-notifications`

Security

Variable	Required	Description	Default
`EMAIL_RATE_LIMIT_PER_SECOND`	No	Override the email sending rate limit, in emails per second. If not set, Sendly automatically fetches the quota from your AWS SES account. When set it is a hard ceiling — it applies whether the SES quota is higher or lower. Fractional values below 1 are supported for deliberately slow sending: `0.16` paces roughly one email every 6.25 seconds (~48 per 5 minutes), which is useful while warming up a new SES account or rebuilding sender reputation. Must be greater than 0.	—

Phishing Detection

Sendly uses AI to detect and block phishing emails before they're sent. This requires an OpenRouter API key — the app fails at startup without one, so that content scanning can never be silently disabled.

Variable	Required	Description	Default
`OPENROUTER_API_KEY`	Yes	OpenRouter API key. Powers outbound phishing detection and inbound spam classification.	—
`OPENROUTER_ASSISTANT_MODEL`	No	LLM model for the AI assistant. See OpenRouter models.	`anthropic/claude-3-haiku`
`OPENROUTER_MODERATION_MODEL`	No	Classification model for phishing/spam scanning. Avoid reasoning models (they can return empty content).	`deepseek/deepseek-v4-flash`
`PHISHING_SAMPLE_RATE_DEFAULT`	No	Percentage of emails to check (0.0-1.0). For example, `0.1` means 10% of emails are analyzed.	`0.1` (10%)
`PHISHING_CONFIDENCE_THRESHOLD`	No	Minimum confidence percentage (0-100) required to auto-disable a project from a single detection.	`85`
`PHISHING_CUMULATIVE_THRESHOLD`	No	Number of phishing detections within the time window required to auto-disable a project.	`3`
`PHISHING_CUMULATIVE_WINDOW_MS`	No	Time window in milliseconds for cumulative phishing tracking.	`3600000` (1 hour)

How it works:

A random sample of emails (controlled by PHISHING_SAMPLE_RATE_DEFAULT) are analyzed by the LLM for phishing content.
Projects are automatically disabled if either:
1. A single email is detected with confidence ≥ PHISHING_CONFIDENCE_THRESHOLD, or
2. PHISHING_CUMULATIVE_THRESHOLD or more emails are flagged within the PHISHING_CUMULATIVE_WINDOW_MS time window.
Detection history is stored in Redis and shared across all worker instances.