config.example.yaml

# SRMTA Configuration File
# Copy to /etc/srmta/config.yaml and adjust for your environment
# Sub-configs in config.d/*.yaml are merged on top of this file (sorted alphabetically)

# Path to config.d/ directory (default: config.d/ next to this file)
config_dir: "/etc/srmta/config.d"

server:
  hostname: "mta1.example.com"
  listen_addr: ":8080"
  max_workers: 100
  shutdown_grace: "30s"

smtp:
  inbound_addr: ":25"           # Port for receiving mail (MX traffic)
  submission_addr: ":587"       # Port for MSA submission (authenticated clients)
  outbound_port: 25             # Remote port used for outbound delivery
  max_connections: 1000
  max_message_size: 52428800  # 50MB
  read_timeout: "60s"
  write_timeout: "60s"
  max_recipients: 100
  require_auth: true
  require_tls: false
  banner_hostname: "mta1.example.com"
  allowed_domains:
    - "example.com"
    - "mail.example.com"
  allowed_domains_file: "/etc/srmta/allowed_domains.ini"  # INI-format domain list
  allowed_ips_file: "/etc/srmta/allowed_ips.ini"          # INI-format IP/CIDR list
  enable_pipelining: true

queue:
  spool_dir: "/var/spool/srmta"
  max_queue_depth: 500000
  max_retries: 9
  retry_intervals:
    - "5m"
    - "15m"
    - "30m"
    - "1h"
    - "2h"
    - "4h"
    - "8h"
    - "16h"
    - "24h"
  dead_letter_after: "72h"
  journal_enabled: true
  shard_count: 16
  domain_buckets: 256
  processing_workers: 50

delivery:
  max_concurrent: 500
  per_domain_concurrency: 20
  connection_timeout: "300s"
  dial_timeout: "30s"
  ehlo_timeout: "30s"
  mail_timeout: "30s"
  rcpt_timeout: "30s"
  data_timeout: "120s"
  pool_size: 50
  pool_idle_timeout: "60s"

dns:
  servers:
    - "8.8.8.8"
    - "8.8.4.4"
    - "1.1.1.1"
  cache_ttl: "300s"
  cache_size: 10000
  timeout: "5s"
  pool_size: 10
  use_redis_cache: false
  enable_dnssec: false

ip_pool:
  ips:
    - address: "203.0.113.10"
      version: 4
      weight: 100
      warm_up: false
      max_rate: 0
      disabled: false
    - address: "203.0.113.11"
      version: 4
      weight: 100
      warm_up: true
      max_rate: 500
      disabled: false
    - address: "2001:db8::1"
      version: 6
      weight: 50
      warm_up: false
      max_rate: 0
      disabled: false
  health_window: "1h"
  disable_threshold: 0.3
  recovery_time: "30m"

dkim:
  enabled: true
  default_key: "example.com:default"
  keys:
    - selector: "default"
      domain: "example.com"
      private_key_path: "/etc/srmta/dkim/example.com.key"
      algorithm: "rsa-sha256"
    - selector: "selector2"
      domain: "mail.example.com"
      private_key_path: "/etc/srmta/dkim/mail.example.com.key"
      algorithm: "rsa-sha256"

bounce:
  hard_bounce_threshold: 0.05    # 5%
  soft_bounce_threshold: 0.15    # 15%
  complaint_threshold: 0.003     # 0.3%
  sender_pause_enabled: true
  suppression_list_enabled: true

logging:
  level: "info"        # debug, info, warn, error
  format: "json"       # json, text
  output: "stdout"     # stdout, file
  file_path: "/var/log/srmta/srmta.log"
  max_size_mb: 100
  max_backups: 10
  max_age_days: 30
  compress: true

metrics:
  enabled: true
  listen_addr: ":9090"
  path: "/metrics"

database:
  host: "${DB_HOST:localhost}"
  port: 5432
  user: "${DB_USER:srmta}"
  password: "${DB_PASSWORD:changeme}"
  dbname: "${DB_NAME:srmta}"
  ssl_mode: "prefer"
  max_open_conns: 25
  max_idle_conns: 5

redis:
  addr: "${REDIS_ADDR:localhost:6379}"
  password: "${REDIS_PASSWORD:}"
  db: 0
  pool_size: 10

tls:
  cert_file: "/etc/srmta/tls/server.crt"
  key_file: "/etc/srmta/tls/server.key"
  ca_file: "/etc/srmta/tls/ca.crt"
  min_version: "1.2"

rate_limit:
  global_rate: 500       # emails/sec
  per_domain_rate: 50    # emails/sec per domain
  per_sender_rate: 100   # emails/sec per sender