Scramd - Synchronous Concurrent Relay and Mailer Daemon

A Simple MTA for forwarding mail that uses synchronous channels to relay mail in realtime.

Features:

• Simple configuration in a single file
• Forwards instantly, no need for queueing

TODO

• Stats Interface
• TLS Support
• Blacklist Support
• RBL
• Greylisting
• DB / key-value store lookups
• RFC Compliant

Why does this even exist ?

I had a requirement for a simple MTA that forwards email for multiple addresses to another address. Managing a full MTA can take a large amount of work and dealing with mail queues can be painful. This is mainly intended for personal use.

Configuration Reference

All configuration is stored in /etc/scramd.yaml

See example_config.yaml for more inspiration

forwards

The forwarding map is configured in YAML as a list of addresses bound to a forwarding address:

forwards:
    target:
     - address1
     - address2
     ...

Example configuration:

---
forwards:
  mailbox1@my.isp:
    - alias@other.dom
    - other.name@mydom.com
  realuser@other.isp:
    - first.last@vanity.domain
    - admin@vanity.domain

hostname

The identifier sent in the SMTP connection banner. (Defaults to the system hostname)

listen_address

The interface address to listen for SMTP requests. (Defaults to 0.0.0.0)

listen_address: 127.0.0.1

listen_port

The TCP Port to listen for SMTP requests. (Defaults to 25)

listen_port: 25

server_timeouts

Set timeouts for the receiving server (the one running at listen_port)

server_timeouts:
    read: 120s
    write: 90s

client_timeouts

Set timeouts when we are sending mail to remote upstream servers

client_timeouts:
    connect: 90s
    read:    30s
    wite:    30s

Contribute

Contributions are very welcome! Feel free to fork and raise a PR aginst this repo

Credits

This is mostly built wtih the help of go-smtpd: https://github.com/bradfitz/go-smtpd

Limitations

• Remote errors cause a connection close with no message after DATA stream. This may cause issues with upstream hosts when the connection is closed unexpectedly.

Licence

MIT © Ian Bissett