Configuration

Posta is configured via environment variables. All variables are prefixed with POSTA_.

Server

Variable	Default	Description
POSTA_PORT	9000	HTTP server port
POSTA_ENV	dev	Environment name
POSTA_DEV_MODE	false	Development mode — stores emails without sending
POSTA_WEB_DIR	web/dist	Path to the dashboard frontend build
POSTA_WEB_URL	—	Public base URL of the Posta instance
POSTA_API_URL	—	Public API base URL advertised in the OpenAPI servers list (optional if POSTA_WEB_URL is set)

Database (PostgreSQL)

Variable	Default	Description
POSTA_DB_HOST	localhost	Database host
POSTA_DB_PORT	5432	Database port
POSTA_DB_USER	posta	Database user
POSTA_DB_PASSWORD	posta	Database password
POSTA_DB_NAME	posta	Database name
POSTA_DB_SSL_MODE	disable	SSL mode (disable, require, verify-full)
POSTA_DB_URL	—	Full connection string (overrides individual settings)

Redis

Variable	Default	Description
POSTA_REDIS_URL	—	Full connection string, e.g. redis://user:pass@host:6379/2. When set, it overrides POSTA_REDIS_ADDR, POSTA_REDIS_USERNAME, POSTA_REDIS_PASSWORD and POSTA_REDIS_DB.
POSTA_REDIS_ADDR	localhost:6379	Redis address (host:port)
POSTA_REDIS_USERNAME	—	Redis ACL username (Redis 6+)
POSTA_REDIS_PASSWORD	—	Redis password
POSTA_REDIS_DB	0	Redis database number to select

Security

Variable	Default	Description
POSTA_JWT_SECRET	—	Required. JWT signing key. Must be changed in production.
POSTA_ADMIN_EMAIL	admin@example.com	Initial admin account email
POSTA_ADMIN_PASSWORD	admin1234	Initial admin account password
POSTA_CORS_ORIGINS	*	Comma-separated allowed CORS origins
POSTA_ENCRYPTION_KEY	—	AES-256-GCM key used to encrypt stored SMTP passwords. Falls back to base64 encoding only when empty.
POSTA_EMAIL_VERIFICATION_REQUIRED	false	Require new users to confirm their email address before they can sign in

Features

Variable	Default	Description
POSTA_OPENAPI_DOCS	true	Enable Swagger/ReDoc API documentation
POSTA_METRICS_ENABLED	false	Enable Prometheus metrics endpoint

note

New-user registration is toggled at runtime from Admin → Settings (the registration_enabled setting), not via an environment variable.

Rate Limiting

Variable	Default	Description
POSTA_AUTH_RATE_LIMIT_ENABLED	true	Enable rate limiting on login/register endpoints
POSTA_RATE_LIMIT_HOURLY	100	Maximum emails per hour per user
POSTA_RATE_LIMIT_DAILY	1000	Maximum emails per day per user

Worker

Variable	Default	Description
POSTA_EMBEDDED_WORKER	false	Run the worker within the API server process
POSTA_WORKER_CONCURRENCY	10	Number of worker goroutines
POSTA_WORKER_MAX_RETRIES	5	Maximum retry attempts per email
POSTA_WORKER_HEALTH_ENABLED	true	Serve /healthz, /readyz and /metrics from a dedicated worker
POSTA_WORKER_HEALTH_PORT	POSTA_PORT	Port for those endpoints. Server and worker run as separate containers, so sharing the number is safe and means one health check for both

Webhooks

Variable	Default	Description
POSTA_WEBHOOK_MAX_RETRIES	3	Maximum webhook delivery retries
POSTA_WEBHOOK_TIMEOUT_SECS	10	Webhook HTTP request timeout (seconds)
POSTA_WEBHOOK_PROXY_URL	—	Optional HTTP/HTTPS/SOCKS5 proxy for outbound webhook delivery

Delivery

Variable	Default	Description
POSTA_AUTO_SUPPRESS_ON_REJECT	true	Add a recipient to the suppression list (and stop retrying) after a permanent 5xx rejection at RCPT TO, e.g. 550 user unknown

Email Verification

Controls the POST /api/v1/emails/verify endpoint (syntax, MX, disposable & role-account checks). Results are cached in Redis.

Variable	Default	Description
POSTA_EMAIL_VERIFY_ENABLED	true	Enable the email verification endpoint
POSTA_EMAIL_VERIFY_CACHE_TTL_HOURS	168	How long an address-level result is cached, in hours (default 7 days)
POSTA_EMAIL_VERIFY_MX_CACHE_TTL_HOURS	24	How long a domain's MX lookup is cached, in hours
POSTA_EMAIL_VERIFY_RATE_HOURLY	1000	Per-user hourly cap on verification requests (0 disables the limit)

OAuth / SSO

Variable	Default	Description
POSTA_GOOGLE_OAUTH_CLIENT_ID	—	Google OAuth client ID for SSO login
POSTA_GOOGLE_OAUTH_CLIENT_SECRET	—	Google OAuth client secret
POSTA_OAUTH_CALLBACK_URL	—	OAuth callback base URL (optional if POSTA_WEB_URL is set)

System SMTP

Outbound SMTP server used for platform notifications (daily reports, invitations, password resets, security alerts). HOST and FROM must both be set for it to activate.

On boot, Posta provisions these settings as a real SMTP server inside the built-in Posta System workspace, so they are visible and testable from the dashboard rather than only readable from the deployment's environment. See Workspaces.

The connection fields — host, port, username, password, encryption — are re-synced from the environment on every restart, so rotating a credential means changing it here and restarting. The server's label and status belong to the operator and survive a restart.

Variable	Default	Description
POSTA_SYSTEM_SMTP_HOST	—	SMTP server host
POSTA_SYSTEM_SMTP_PORT	587	SMTP server port
POSTA_SYSTEM_SMTP_USERNAME	—	SMTP username
POSTA_SYSTEM_SMTP_PASSWORD	—	SMTP password
POSTA_SYSTEM_SMTP_FROM	—	From address for platform notifications
POSTA_SYSTEM_SMTP_ENCRYPTION	starttls	Encryption mode: none, ssl, or starttls

Blob Storage

Where email attachments are stored. Leave POSTA_BLOB_PROVIDER empty to disable external attachment storage.

Variable	Default	Description
POSTA_BLOB_PROVIDER	—	Storage backend: s3 or filesystem
POSTA_BLOB_S3_ENDPOINT	—	S3-compatible endpoint (e.g. MinIO, R2)
POSTA_BLOB_S3_REGION	us-east-1	S3 region
POSTA_BLOB_S3_BUCKET	—	S3 bucket name
POSTA_BLOB_S3_ACCESS_KEY	—	S3 access key
POSTA_BLOB_S3_SECRET_KEY	—	S3 secret key
POSTA_BLOB_S3_USE_SSL	true	Connect to S3 over TLS
POSTA_BLOB_S3_PATH_STYLE	false	Use path-style addressing (required by some MinIO setups)
POSTA_BLOB_FS_PATH	data/attachments	Storage path when using the filesystem provider

Inbound Email

Variable	Default	Description
POSTA_INBOUND_ENABLED	false	Master toggle — enables the SMTP receiver and the /api/v1/inbound/* routes
POSTA_INBOUND_SMTP_HOST	0.0.0.0	Bind address for the built-in SMTP receiver
POSTA_INBOUND_SMTP_PORT	2525	SMTP listener port (use 25 publicly)
POSTA_INBOUND_HOSTNAME	posta.local	Hostname announced in EHLO / used as TLS SNI — should match the MX record
POSTA_INBOUND_MAX_MESSAGE_SIZE	26214400	Max raw message size in bytes (default 25 MiB)
POSTA_INBOUND_MAX_ATTACH_SIZE	10485760	Max per-attachment size in bytes (default 10 MiB)
POSTA_INBOUND_WEBHOOK_SECRET	—	Shared secret for the MX-provider webhook at POST /api/v1/inbound/webhook (sent via X-Posta-Inbound-Secret)
POSTA_INBOUND_TLS_MODE	none	SMTP TLS mode: none or starttls
POSTA_INBOUND_TLS_CERT_FILE	—	PEM cert path (required when TLS mode is starttls)
POSTA_INBOUND_TLS_KEY_FILE	—	PEM key path (required when TLS mode is starttls)
POSTA_INBOUND_SMTP_RATE_LIMIT	60	Per-IP max SMTP sessions per window (0 disables)
POSTA_INBOUND_SMTP_RATE_WINDOW	60	Rate-limit window in seconds

Web Form Messages

Variable	Default	Description
POSTA_MESSAGES_ENABLED	false	Master toggle — enables the public /api/v1/f/{key} ingest endpoint and the messages routes
POSTA_MESSAGES_MAX_BODY_BYTES	65536	Max submission body size in bytes (each form can lower it)
POSTA_MESSAGES_MAX_ATTACH_SIZE	5242880	Max per-attachment size in bytes (attachments are off per form by default)
POSTA_MESSAGES_IP_RATE_LIMIT	20	Per-IP submissions per window (0 disables — leaves a public endpoint unthrottled)
POSTA_MESSAGES_IP_RATE_WINDOW	3600	Rate-limit window in seconds
POSTA_MESSAGES_PER_FORM_HOURLY	200	Submissions allowed per form per hour
POSTA_MESSAGES_PER_EMAIL_HOURLY	5	Submissions allowed per sender address per hour, per form
POSTA_MESSAGES_PER_WORKSPACE_DAILY	1000	Submissions allowed per workspace per day
POSTA_MESSAGES_INBOUND_DOMAIN	—	Domain for msg+<token>@ reply addressing so email answers rejoin the thread (requires POSTA_INBOUND_ENABLED=true)

Advanced

Variable	Default	Description
POSTA_ALLOW_DOWNGRADE	false	Allow the server to boot when the binary version is older than the version recorded in the database
POSTA_PLAN_ENFORCEMENT	false	Enforce hosted plan limits / quotas

Example .env File

# Server
POSTA_PORT=9000
POSTA_ENV=production

# Database
POSTA_DB_HOST=localhost
POSTA_DB_USER=posta
POSTA_DB_PASSWORD=secure-password
POSTA_DB_NAME=posta
POSTA_DB_PORT=5432

# Redis
POSTA_REDIS_ADDR=localhost:6379

# Security
POSTA_JWT_SECRET=your-very-long-random-secret-key
POSTA_ADMIN_EMAIL=admin@yourdomain.com
POSTA_ADMIN_PASSWORD=strong-admin-password
POSTA_CORS_ORIGINS=https://dashboard.yourdomain.com

# Features
POSTA_METRICS_ENABLED=true

# Rate Limiting
POSTA_AUTH_RATE_LIMIT_ENABLED=true
POSTA_RATE_LIMIT_HOURLY=500
POSTA_RATE_LIMIT_DAILY=5000

# Worker
POSTA_EMBEDDED_WORKER=true
POSTA_WORKER_CONCURRENCY=20