This script converts an alias file to a sieve script for stalwart-mail.

All local-parts are considered to be case-insensitive.

Usage

Given an alias file testdata/example.aliases that contains lines of redirects of the form local-part with optional @fqdn followed by a space followed by a list (space or comma+space separated) list of destinations that consist of a local-part and optionally an @fqdn. If you don't define an fqdn along any of the addresses, the default domain from your commandline input will be appended.

An example using the testdata directory of this repository:

$ ./alias_to_sieve testdata/example.aliases example.com

require ["variables", "copy", "vnd.stalwart.expressions", "envelope", "editheader"];

let "i" "0";
while "i < count(envelope.to)" {
  let "redirected" "false";
  if eval "eq_ignore_case(envelope.to[i], '[email protected]')" {
    addheader "Delivered-To" "[email protected]";
    redirect :copy "[email protected]";

    deleteheader :index 1 :is "Delivered-To" "[email protected]";
    let "redirected" "true";
  }
  if eval "eq_ignore_case(envelope.to[i], '[email protected]')" {
    addheader "Delivered-To" "[email protected]";
    redirect :copy "[email protected]";

    deleteheader :index 1 :is "Delivered-To" "[email protected]";
    let "redirected" "true";
  }
  if eval "eq_ignore_case(envelope.to[i], '[email protected]')" {
    addheader "Delivered-To" "[email protected]";
    redirect :copy "[email protected]";

    deleteheader :index 1 :is "Delivered-To" "[email protected]";
    let "redirected" "true";
  }
  if eval "eq_ignore_case(envelope.to[i], '[email protected]')" {
    addheader "Delivered-To" "[email protected]";
    redirect :copy "[email protected]";

    deleteheader :index 1 :is "Delivered-To" "[email protected]";
    let "redirected" "true";
  }
  if eval "eq_ignore_case(envelope.to[i], '[email protected]')" {
    addheader "Delivered-To" "[email protected]";
    redirect :copy "[email protected]";
    redirect :copy "[email protected]";

    deleteheader :index 1 :is "Delivered-To" "[email protected]";
    let "redirected" "true";
  }
  if eval "eq_ignore_case(envelope.to[i], '[email protected]')" {
    addheader "Delivered-To" "[email protected]";
    redirect :copy "[email protected]";
    redirect :copy "[email protected]";
    redirect :copy "[email protected]";

    deleteheader :index 1 :is "Delivered-To" "[email protected]";
    let "redirected" "true";
  }
  if eval "!redirected" {
    let "destination" "envelope.to[i]";
    redirect :copy "${destination}";
  }
  let "i" "i+1";
}
discard;

If you have multiple domains with multiple alias files, pass them all in one run: $ ./alias_to_sieve simple.aliases example.com example.aliases example.org.

Limitations

You cannot use apostrophes (') in any mail addresses although allowed by RFC 5322 since they would break termination of strings in sieve.

This parser is not designed with security in mind. While the above gives some basic protection against code injection, I have no idea whether sieve has other pitfalls that might allow them.

This is my first rust project, consume the code with care.

The generated code is specific to stalwart-mail and contains non-standard sieve features.

Configure stalwart-mail to use it

You need to use a stalwart version of at least 0.12.0.

1. Run this program and save its outputs to a file (e.g. /tmp/virt_aliases).
2. Include the following in your configuration TOML:

[config]
 # We here define what comes from the TOML-file and especially add "sieve.trusted.*" to the default ones
 # because only TOML-based keys may use macros to load files from disk.
 # We want this to be able to load our sieve-script for mail forwarding.
 # See https://stalw.art/docs/configuration/overview/#local-and-database-settings for more details.
local-keys = [
    …
    "sieve.trusted.*",
]

[session.data]
script = "'redirects'"

[sieve.trusted]
return-path = "sender"

 # should be at least max-recipients times the length of your largest alias forwarding list.
[sieve.trusted.limits]
out-messages = 500
redirects = 500

[sieve.trusted.scripts.redirects]
contents = "%{file:/tmp/virt_aliases}%"

[[sieve.trusted.sign]]
if = "is_local_domain('', sender_domain)"
then = "['rsa-' + sender_domain, 'ed25519-' + sender_domain]"

[[sieve.trusted.sign]]
else = false

 # Otherwise stalwart rejects mail for redirects because it does not know the recipient account. 
[session.rcpt]
catch-all = true

3. Create the local domains in the web-admin.
4. Create a catch-all account. It does not receive mail that is directed towards redirects but otherwise works as a catch-all account.