Configuration

MXHook is configured via environment variables or CLI flags. CLI flags take precedence over environment variables.

Environment Variables

Variable	CLI Flag	Default	Description
MXHOOK_SMTP_ADDR	--smtp-addr	0.0.0.0:2525	SMTP server listen address
MXHOOK_SMTP_DOMAIN	--smtp-domain	localhost	SMTP server hostname (used in HELO/EHLO)
MXHOOK_API_ADDR	--api-addr	0.0.0.0:8080	REST API listen address
MXHOOK_POSTGRES_DSN	--db-url	—	PostgreSQL connection string (required)
MXHOOK_API_KEY	--api-key	—	API authentication key. If empty, API is unauthenticated
CF_QUEUE_ACCOUNT_ID	—	—	Cloudflare account ID (for Cloudflare Queue backend)
CF_QUEUE_ID	—	—	Cloudflare queue ID
CF_QUEUE_TOKEN	—	—	Cloudflare API token

Example .env File

# SMTP
MXHOOK_SMTP_ADDR=0.0.0.0:25
MXHOOK_SMTP_DOMAIN=mail.yourdomain.com

# API
MXHOOK_API_ADDR=0.0.0.0:8080
MXHOOK_API_KEY=your-secret-api-key

# Database
MXHOOK_POSTGRES_DSN=postgres://mxhook:mxhook@localhost:5432/mxhook?sslmode=require

SMTP Limits

Limit	Default	Description
Max message size	10 MB	Maximum size of a single email message
Max recipients	50	Maximum number of recipients per message
Rate limit	100 msgs/hour per IP	Inbound rate limiting

PostgreSQL

MXHook requires PostgreSQL 14 or later. The connection string follows the standard libpq format:

postgres://user:password@host:port/database?sslmode=disable

MXHook automatically creates the required tables on first startup. No manual migration is needed.

Queue Backend

By default, MXHook uses PostgreSQL as its message queue (recommended for most deployments). For edge/serverless deployments, you can use Cloudflare Queues by setting the CF_QUEUE_* variables.