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mi-poop-mail

This is a machine image for an e-mail server based on Exim, Dovecot, Clamav and Spamassassin. It is suitable mostly for low to medium-volume use, such as for personal use or a small business.

Please refer to https://github.com/joyent/mibe for use of this repo.

Use with base-64 image from Joyent; tested with 15.4.0.

Metadata

The following customer_metadata is used:

  • dovecot:qualify_domain - Domain to use as the authentication realm if the client presents none (default: none)
  • dovecot:primary_hostname - Hostname to use for TLS (default: system hostname)
  • exim:qualify_domain: - Domain to append to addresses when only a local_part is given
  • system:ssh_disabled - Whether or not to disable the ssh daemon (default: false)
  • system:timezone - What timezone to use
  • backup:increments: How many daily backup increments before a new full backup is made (default: 28)
  • backup:retain: How long backups are retained, in weeks (default: '8)
  • backup:openssl_key: aes-128-cbc key to encrypt backup tarballs with before uploading (128-bit hex)
  • backup:openssl_iv: see above, but iv
  • backup:bucket: what bucket to use (example: gs://my-mail-backup)
  • boto:gs_oauth2_refresh_token: the "gs_oauth2_refresh_token" setting from boto.cfg to access google cloud storage
  • boto:default_project_id: the "default_project_id" setting from boto.cfg to specify what GCS project to use

Services

When running, the following services are exposed to the network on both IPv4 and IPv6:

  • 25, 587: SMTP (tls required for authentication)
  • 143, 993: IMAP (tls required)
  • 4190: ManageSieve (tls required)
  • 22: SSH (if not disabled)
  • 80: web (briefly, when requesting Let's Encrypt certificates only.)

Data

This image requires a delegated dataset. It will be mounted at /srv/mail and will store user mailboxes. Also on this dataset is the user information:

  • /srv/mail/passwd/<domain>: users per domain, formatted as user:passwd where passwd can be had using 'doveadm pw'
  • /srv/mail/aliases/<domain>: aliases per domain, formatted as user:destination

TLS certificates from Let's Encrypt are used. They are stored on the delegated dataset in /srv/mail/ssl/acme. Acmetool is used to request them. By default the dovecot primary_hostname and system hostname are requested in a single cert. To request more certificates, use acmetool want.

Exim keeps its spool in /srv/mail/exim/spool so it is preserved upon reprovision. Also there are some configuration lists in /srv/mail/exim/conf:

  • global_aliases: aliases that exist in all handled domains. Suggested use is for a 'postmaster' alias.
  • rewrite_domains: domains to rewrite to another domain, as domain: newdomain
  • relay_from_hosts: hosts to relay for without authentication
  • relay_to_domains: domains to be a secondary mx for, or otherwise relay to without authentication
  • senderverify_exceptions: e-mail addresses to accept (on 'MAIL FROM:') without doing a verification callout
  • dkim_required: domains (wildcard-matched) for which a valid DKIM signature is required to accept e-mail

Dovecot allows local configuration in /srv/mail/dovecot/conf/local.conf. This can be used for example to add an imapc config to migrate mail from another server.

A script is run nightly to create incremental tar-based backups and upload them to Google Cloud Storage. This should be adaptable to S3-based storage with minimal effort if necessary. It encrypts the tar files using openssl aes-128-cbc before uploading them, and saves the most recent tar in /srv/mail/backups for immediate use. If any of the required metadata keys (key, iv, bucket) are not set, the script will not run.

Example JSON

{
  "brand": "joyent",
  "image_uuid": "",
  "alias": "poopmail",
  "hostname": "poopmail",
  "dns_domain": "poop.nl",
  "max_physical_memory": 1536,
  "cpu_shares": 100,
  "quota": 100,
  "delegate_dataset": "true",
  "nics": [
    {
      "nic_tag": "admin",
      "ips": ["1.2.3.4/24", "2001::1/64"],
      "gateways": ["1.2.3.1"],
      "primary": "true"
    }
  ],
  "resolvers": [
    "8.8.8.8",
    "8.8.4.4"
  ],
  "customer_metadata": {
    "system:ssh_disabled": "true",
    "system:timezone": "Europe/Amsterdam",
    "dovecot:qualify_domain": "cyberhq.nl",
    "dovecot:primary_hostname": "mail.poop.nl"
  }
}